RenewCMS/docs/api.md

# API reference

The full, searchable reference is the Integration page of the running app (`/integration`). It
renders `web/src/data/apiCatalogue.ts`, which is the single source for this page. This file is for
readers without the UI. Reading articles (pagination, `format`, body schemas) has its own page,
[api/articles.md](api/articles.md), and API keys are covered in [api/api-keys.md](api/api-keys.md).

## Base URL
The origin that serves the app, for example `https://cms.example`. Every path starts with `/v1`,
for example `https://cms.example/v1/article/`.

## Authentication
- Public routes need nothing: `GET /v1/article/`, `GET /v1/article/{id}`, `GET /v1/article/{id}/seo`
  and `GET /v1/site/{key}/sitemap`. They return online articles only; the list and the resolved SEO
  object also answer drafts to a verified session or API key.
- Everything else needs a signed-in browser session (the `jwt` cookie) or an API key:
  `Authorization: Bearer rcms_...`. Create keys at `/integration/api-keys`. A key acts as its
  creator, with that user's role, and shows in full once.
- A key cannot call `POST /v1/auth/verify`, `DELETE /v1/auth/register`, `/v1/api-key/*` or
  `/v1/system/*`. Those answer 403 "This action needs a real session." An invalid, unknown, expired
  or revoked key answers 401, even on public routes. The site writes (`POST`, `PATCH` and `DELETE`
  under `/v1/site`) and the author writes (`POST`, `PATCH` and `DELETE` under `/v1/author`, `POST /v1/author/me` included) are session only too.
- Each key can make 120 requests per minute. Beyond that: 429 with a `Retry-After` header.

## Routes a key can call (29)
| Group | Routes |
| --- | --- |
| Articles | GET /v1/article/, GET /v1/article/{id}, GET /v1/article/{id}/seo, POST /v1/article/{id}/seo/check, POST /v1/article/, PATCH /v1/article/{id}, PATCH /v1/article/{id}/publish, PATCH /v1/article/{id}/unpublish, DELETE /v1/article/{id} |
| Media | GET /v1/media/, POST /v1/media/, PATCH /v1/media/{id}, DELETE /v1/media/{id}, POST /v1/media/merge, GET /v1/media/{id}/usage, GET /v1/media/purge-settings (owner or admin), PATCH /v1/media/purge-settings (owner or admin), GET /v1/media/purge-preview (owner or admin), POST /v1/media/purge (owner or admin), GET /v1/media/{id}/variants (owner or admin, session only), POST /v1/media/{id}/variants (owner or admin, session only), POST /v1/media/{id}/variants/{name} (owner or admin, session only), DELETE /v1/media/{id}/variants/{name} (owner or admin, session only) |
| Users and invites | GET /v1/user/, PATCH /v1/user/me, POST /v1/user/invite (owner only), DELETE /v1/user/invite/{id} (owner only), POST /v1/user/invite/{id}/renew (owner only), GET /v1/auth/me (with the linked `author`) |
| Settings | GET /v1/settings |
| Sites | GET /v1/site/, GET /v1/site/{key}/sitemap |
| Authors | GET /v1/author/ |

## Activity log
The activity routes are session only: a key answers 403 "This action needs a real session." and a
key never reads the audit trail. Events are append-only; there is no `POST`, `PUT`, `PATCH` or
`DELETE` under `/v1/activity`.

| Route | Who | Purpose |
| --- | --- | --- |
| `GET /v1/activity` | Any verified user | Filtered, paged events. Owner and admin see every event; any other role is scoped to its own events, and `actor` set to someone else answers 403 "Only owners and admins can do this." |
| `GET /v1/activity/summary` | Owner, admin | Counts for the range, the previous period, active people and seven-bucket series. |
| `GET /v1/activity/export` | Owner, admin | The same filters as the list without `page` or `size`, as a `text/csv; charset=utf-8` attachment (`when,actor,action,target,outcome,source,ip`). Cells starting with `=`, `+`, `-` or `@` get a leading quote. |

Query: `q`, `actor` (`user:ID`, `key:ID`, `system`), `category` (`articles`, `media`, `users`,
`api_keys`, `auth`, `system`, `sites`, `authors`), `outcome` (`all`, `success`, `failed`), `security` (`true`), `range`
(`today`, `7d`, `30d`, `all`, `custom`; default `7d`), `from` and `to` (dates, with `custom`), `page` (from
1) and `size` (25, 50 or 100). Any invalid value answers 400 with the body-mismatch message. Dates
are UTC. The list answers `{ items, total, page, size }`, newest first (`created_at`, then `id`).

`GET /v1/settings` also returns `activity_retention_days` (30, 90, 365 or 0 for forever, default
90), `activity_retention_max_gb` (0 for no size limit), `activity_log_size_bytes`,
`activity_last_cleanup_at` and `activity_last_cleanup_removed`. `PATCH /v1/settings` with
`{"activity_retention_days": 30}`, `{"activity_retention_max_gb": 5}` or both is session only and
owner only (403 "Only the owner can do this."); any other value answers 400. The daily cleanup
removes events past the age limit, then the oldest events until the log fits the size limit.
Whichever limit is reached first wins.

### What is recorded
Every real action is recorded by its use case, once, after the change was made (outcome `success`)
or after the use case refused it (outcome `failed`, with a plain `failure_reason`). Nothing is
recorded for a read (no `GET`, no list, no public article read, no status poll), for a request that
fails validation, or for a target that does not exist (404). A failed audit write is logged and
never changes the response or the change itself.

| Category | Actions |
| --- | --- |
| `articles` | `article.create`, `article.edit`, `article.publish`, `article.unpublish`, `article.delete` |
| `media` | `media.upload`, `media.rename`, `media.delete`, `media.merge`, `media.purge`, `media.variant_create`, `media.variant_update`, `media.variant_delete`, `media.variant_enable`, `media.variant_disable`, `media.variant_purge`, `media.variant_generate_all`, `media.variant_purge_image`, `media.variant_purge_all`, `media.variant_purge_unused` |
| `users` | `user.register`, `user.verify`, `user.update_profile`, `invite.create`, `invite.cancel`, `invite.renew`, `invite.accept` |
| `sites` | `site.create`, `site.edit`, `site.set_default`, `site.delete` |
| `authors` | `author.create`, `author.edit`, `author.delete` |
| `system` | `system.media_purge` (scheduled), `system.update_checked`, `system.update_downloaded`, `system.restart_requested`, `system.activity_cleanup`, `system.activity_retention_changed` |

Target types: `article`, `site`, `author`, `image`, `image_variant` (id and name are the variant name), `user`, `invite`,
`api_key` and `release` (id and name are the tag).
Only the fields `title`, `online`, `body`, `site`, `name`, `base_url`, `default_robots`, `locale`, `default_social_image`, `slug`, `canonical_url`, `noindex`, `cover_image`, `social_image`, `excerpt`, `seo_title`, `seo_description`, `social_title`, `social_description`, `cover_image_alt`, `site_name`, `title_template`, `default_description`, `bio`, `website`, `social_links`, `avatar`, `user`, `authors`, `filename`, `display_name`, `width`, `height`, `fit`, `format` and `quality` appear in `changes` (a site key is never a change; moving an article records `site` with the site names; changing the credited authors records `authors` with the names in order; the `user` change of an author holds usernames, never an email), with the
kinds `text` and `body`; a body edit carries a signed character count delta and never the text; the free-text SEO fields (`excerpt`, `seo_title`, `seo_description`, `social_title`, `social_description`, `cover_image_alt`) do the same under their own field name, while `slug`, `canonical_url`, `noindex`, `cover_image`, `social_image` (image file names) and the site fields `site_name`, `title_template`, `default_description` carry `before` and `after`. `seo_dismissed` is not an edit and records nothing. A
change that leaves a value as it was (same body, same publish state, same file name, same display
name) records nothing. Params: `media.merge` and `media.purge` and `system.media_purge` carry
`merged` and `articles_updated`, plus `failed_groups` when a group failed (still outcome `success`);
`media.variant_generate_all` carries `generated`, `failed` and `causes` (a list of `too_large`,
`unsupported_format` or `failed`) and is `failed` only when nothing was generated and something failed;
`media.variant_purge_image` carries `purged_files` and `purged_bytes`; both have an `image` target
and are recorded only when files were generated or removed;
`media.variant_purge_all` and `media.variant_purge_unused` (no target) carry `purged_files` and
`purged_bytes`, the latter also `older_than_days`; a partial purge adds `failed_files` and stays
`success`, and a purge that removed nothing while some files failed is `failed`; nothing is recorded
when no file was removed or failed;
`system.update_checked` carries `update_available`; `system.restart_requested` carries `kind` and,
for an update, `tag` (it has no target). `system.update_downloaded` is recorded when the job reaches
`ready` or `failed`, with the origin captured at request time; a refusal at the start is recorded
immediately. A failed registration or invite acceptance has an `anonymous` actor named by the
attempted username.

`failure_reason` is one fixed sentence per domain error, matched with `errors.Is`, at most 255
characters, for example "The title must be between 3 and 200 characters.", "That file name is not
valid.", "The merge request is not valid.", "A purge is already running.", "Registration is closed
on this site.", "That invitation has expired.", "The release feed could not be reached." or "The
update could not be downloaded.". Any other error becomes "Something went wrong on our side. Please
try again."; the text of the error never reaches the event, the API or the CSV. Passwords, hashes,
codes, article bodies, file bytes, storage paths and asset urls are never recorded.

Article routes accept `?format=markdown|html|json` (default `markdown`). `GET /v1/media/` accepts
`q`, `hash`, `filter` (`all`, `unused` or `duplicates`), `sort` (`newest`, `oldest`, `name`,
`largest` or `total_size`, the original plus its generated variants), `variants` (`with` or
`without` generated variant files), `page` (a whole number from 1, default 1) and `size` (5, 25, 50
or 100, default 25). The body is `{ "items": [...], "total", "page", "size", "counts" }`: `total` is
the number of images matching `q`, `hash`, `filter` and `variants` before paging, `page` and `size`
echo the values applied, and `counts` (`all`, `unused`, `duplicates`) stays library-wide, ignoring
every filter and the paging. Ordering is applied to the whole matching list before slicing, with the
image id as the final tie-break, so pages never overlap or skip. A page past the last answers 200
with `items: []` and the real `total`. Any invalid `page`, `size`, `filter`, `sort`, `variants` or
`hash` is 400 "The media query is invalid.". Every item carries `variant_count` and `variant_size`
(the index rows of the image and their bytes, 0 when none).

Breaking change: `next_cursor` is gone and no `X-Total-Count` header is sent. `cursor` and `limit`
are no longer parameters; they are ignored, never an error, and have no effect on paging.

## Sites
Every article belongs to exactly one site, and exactly one site is the default. A site is `{ id,
name, key, base_url, default_social_image_id, default_robots, locale, is_default, article_count }`:
`name` is 1 to 100 characters, `key` is 2 to 32 characters of lowercase letters, digits and single
dashes (`^[a-z0-9]+(-[a-z0-9]+)*$`) and never changes, `base_url` is `https` (or `http` for
`localhost`, `127.0.0.1` and `[::1]`) with no path, query or user info (a trailing slash is
stripped, uniqueness is not enforced), `default_robots` is `index` (default) or `noindex`, `locale`
is `null` or a tag such as `en` or `fr-CA` (an empty string means none) and `default_social_image_id`
is `null` or the id of an image. Read access needs a verified session or an API key; every write is
session only and owner only (403 "Only the owner can do this.", or "This action needs a real
session." with a key). The role is checked before the body.

| Route | Purpose |
| --- | --- |
| `GET /v1/site/` | The sites, default first and then by name, each with `article_count`. |
| `POST /v1/site/` | Create. 201 with the site. `is_default: true` makes it the default. `site_name`, `title_template` and `default_description` are optional and validated like on `PATCH`. |
| `PATCH /v1/site/{id}` | Edit `name`, `base_url`, `default_robots`, `locale`, `default_social_image_id`, `site_name`, `title_template`, `default_description`. Absent fields are untouched. `key` may only be repeated unchanged; `is_default` is refused. |
| `PATCH /v1/site/{id}/default` | Make the site the default, atomically. Setting the current default is a no-op. |
| `DELETE /v1/site/{id}?reassign_to={id}` | 204. A site with articles needs `reassign_to`; the articles move and the site is deleted in one transaction. `reassign_to` is ignored when the site has no article. |

Errors are plain text whose body is exactly the token: 409 `site_key_taken`, 409 `site_has_articles`,
403 `default_site` (checked before the articles), 400 `key_immutable`, 400 `invalid_site_url`, 400
`invalid_locale`, 400 `invalid_title_template`, 400 `image_not_found`, 400 `use_set_default`, 400 `invalid_reassign` (missing
number, the site itself or not a whole number) and 404 `site_not_found`. Refused writes except `site_not_found` and `image_not_found` are recorded as failed events. A body that cannot be
decoded is 400 with the body-mismatch message, a malformed id is 400 with the uint32 message, and a
field that fails validation (`name`, `key` format, `default_robots`, `site_name` over 100 characters, `title_template` over 200, `default_description` over 320) is 400 with the validator text.

A site also carries `site_name` (at most 100 characters, `""` by default), `title_template` (at most 200 characters, `%title% | %site%` by default; it must contain `%title%`, case sensitive, otherwise 400 `invalid_title_template`, an empty template included) and `default_description` (at most 320 characters, `""` by default). They appear on every site response, `POST` accepts them and `PATCH` edits them like the other site fields. Existing sites get the defaults when the server starts after the upgrade.

Articles carry `site_id`. A new article starts on the default site. `GET /v1/article/?site=<key>`
keeps only the articles of that site and composes with `status`, `q`, `sort`, `size` and `page`;
`counts` stay global, an unknown key answers 200 with no item and an empty `site=` is 400 with the
body-mismatch message. `PATCH /v1/article/{id}` takes `body`, `site_id`, `author_ids` and the SEO
fields below, and nothing else, such as `title`: absent fields are untouched, an empty object, an object without
those fields, a `null` value (except on `cover_image_id` and `social_image_id`) or a malformed value is 400 with the body-mismatch message, `site_id: 0` is
400 with the validator text and an unknown site is 404 `site_not_found`. Moving an article never
changes `is_online`. `{"body": ""}` still sets an empty body, but `{}` and `{"body": null}` no longer do: they are 400.

### Resolved SEO, check, list status and sitemap

RenewCMS renders no page and injects no meta tag: it returns the data a frontend needs.

| Route | Who | Purpose |
| --- | --- | --- |
| `GET /v1/article/{id}/seo` | public for online articles; a verified session or API key also reads drafts | The resolved object `{ title, description, canonical_url, robots, og, twitter, image, authors, published_at, modified_at, fallbacks, json_ld }`. It never carries the body, the id or `seo_dismissed`, ignores `format`, and writes nothing. An offline article for any other caller, and a missing one, is 404 `Article not found`. |
| `POST /v1/article/{id}/seo/check` | verified session or API key (401 without credentials, 403 unverified) | Evaluates the article without saving. The body is `{}` or any of the twelve SEO fields of `PATCH` plus `body`; each replaces the saved value for this check only. `site_id`, `author_ids`, unknown fields and `null` (except on `cover_image_id` and `social_image_id`) are 400 with the body-mismatch message. The other validation is the one of `PATCH` (`invalid_slug`, `invalid_url` as 422, `image_not_found`, validator text). Answers `{ status, suggestions, slug }` where `suggestions` is `[{ code, field, params }]` and `slug` is `{ available, suggestion }`. A taken slug is a 200 with `available: false` and the first free `<slug>-N` in `suggestion`, never a 409. |
| `GET /v1/site/{key}/sitemap` | public | A JSON array `[{ url, modified_at, noindex }]` of the online articles of the site with that key, by id ascending. `url` is `base_url/slug` (never the canonical override). `page` (default 1) and `size` (25, 50, 100 or 500, default 100); an invalid value is 400 with the body-mismatch message. The total is in the `X-Total-Count` header. An unknown key, an id included, is 404 `site_not_found`. |

`GET /v1/article/` also takes `seo=ready|suggestions|hidden` (any other value, an empty one included, is 400 with the body-mismatch message, after the `format` check). It is applied before paging and composes with `q`, `status`, `site`, `sort`, `page` and `size`; `total` follows it and `counts` ignore it. Every item carries `seo_status` (`ready`, `suggestions` or `hidden`) and `seo_suggestions` (the number of suggestions that are not dismissed). The filter is evaluated in memory over every matching article, so its cost grows with the number of articles on the site; without it only the returned page is assessed.

`X-Total-Count` is added to `Access-Control-Expose-Headers` next to `Link`, so a browser on an allowed origin can read it.

### Article SEO fields

An article carries twelve search and sharing fields, all edited through `PATCH /v1/article/{id}` and returned by
every single-article read (`GET /v1/article/{id}`, `POST`, `PATCH`, `publish`, `unpublish`):
`slug`, `excerpt`, `seo_title`, `seo_description`, `cover_image_id`, `cover_image_alt`, `social_title`,
`social_description`, `social_image_id`, `canonical_url`, `noindex` and `seo_dismissed`. Text fields are `""`
when empty, the two image ids are `null` when unset, `noindex` is `false` and `seo_dismissed` is `[]` by
default. Each item of `GET /v1/article/` carries `excerpt` and `slug` and none of the other ten.
The limits are counted in characters: `excerpt` 300, `seo_title` 120, `seo_description` 320,
`cover_image_alt` 200, `social_title` 120, `social_description` 320, `canonical_url` 2048; going over is
400 with the validator text. `cover_image_id` and `social_image_id` accept `null` (and only those two do);
`0` is 400 with the validator text and an unknown image is 400 `image_not_found`. `canonical_url` is `""` or an absolute
`https` URL with a host, otherwise 422 `invalid_url`. `seo_dismissed` is a list of the codes `title_long`,
`title_empty`, `desc_short`, `desc_long`, `cover_alt`, `cover_none`, `slug_long`, `no_au`, `no_h`, `body_alt`
and `short`: an unknown code is 400 with the validator text and duplicates are collapsed with the order
kept. `noindex` is only a flag, it does not take the article offline.

The `slug` matches `^[a-z0-9]+(-[a-z0-9]+)*$` with 1 to 100 characters (400 `invalid_slug`) and is unique per
site, never globally. It is generated from the title when the article is created: lowercase, accents folded,
every run of other characters becomes one dash, dashes trimmed, cut to 100 characters, and `article` when no
letter or digit is left; a slug already used on the site gets `-2`, `-3`... silently. The same rule
backfills the existing articles when the server starts after the upgrade (in id order within each site, so
the oldest article keeps the plain slug). Sending `slug: ""` regenerates the slug from the title. A slug
used by another article on the target site (the new site when `site_id` is sent too, and a move re-checks
the current slug) is 409 with the plain-text body `slug_taken`; the response then carries the header
`X-Slug-Suggestion` holding the first free `<slug>-N` from 2 on that site, fitting 100 characters. The header
is set on this 409 only, never on another response. A regeneration that collides is refused the same way, never suffixed
silently. Saving an article with its own slug is not a collision. Publishing never changes a slug, a deleted article
frees its slug.

New error tokens are plain text from the handler: 409 `slug_taken`, 400 `invalid_slug`, 422 `invalid_url`, 400
`image_not_found` and 400 `invalid_title_template` (sites). Edits that change a SEO field are recorded as
`article.edit` events (`slug`, `canonical_url`, `noindex`, `cover_image`, `social_image` with before and after;
the free-text fields as a size delta only); a refused slug is recorded as failed.

A site's `default_social_image_id` counts as a use of that image: it raises `used_in` and keeps the
image out of the `unused` filter. Deleting the image sets the field to `null` and succeeds. `POST /v1/media/merge` and `POST
/v1/media/purge` repoint the sites of the merged copies to the kept image and report it as
`sites_updated` next to `articles_updated`.

An article's `cover_image_id` and `social_image_id` count the same way. `used_in` counts every article that uses the
image in its body, as cover or as social image once, plus the authors using it as an avatar and the sites using it as default
social image. Deleting an image never fails because of its uses: the covers and social images pointing at it are set to `null`
(the `cover_image_alt` and the bodies are untouched), and a failed delete leaves every reference in place. A merge or a purge repoints
the covers and social images of the copies to the kept image, and an article rewritten in its body and its cover counts once in
`articles_updated`.

`GET /v1/media/{id}/usage` stays an array. Every item keeps the keys it had and gains `type` (`article`,
`author` or `site`) and `fields`. An article item is `{ "type": "article", "id", "title", "published", "fields" }` with
`fields` from `body`, `cover` and `social` (one item per article, in that order); an author item is
`{ "type": "author", "id", "title": <name>, "fields": ["avatar"] }` and a site item is `{ "type": "site", "id", "title": <name>,
"fields": ["default_social_image"] }`; author and site items have no `published` key. The array is `[]` for an unused image.

## Authors

An author is a public byline, with or without an account. It is `{ id, name, slug, bio, avatar_id,
website, social_links, user_id, is_linked, article_count }`, plus `user_email` for owners and admins
only (absent for every other caller). `name` is 1 to 100 characters after trimming, `slug` matches
`^[a-z0-9]+(-[a-z0-9]+)*$` with 1 to 100 characters and is unique (generated from the name when
omitted: accents folded, punctuation runs become one dash, `author` when nothing is left), `bio` has
at most 280 characters (counted in runes), `avatar_id` is `null` or an image id, `website` is `null`
or an `https` URL with a host (an empty string means none, at most 2048 characters),
`social_links` holds at most 5 `{ "type", "url" }` with `type` one of `x`, `linkedin`, `github`,
`mastodon`, `custom` and an `https` URL. `user_id` is the unique link to a user. Zero authors on an
article is allowed and never blocks publishing.

| Route | Who | Purpose |
| --- | --- | --- |
| `GET /v1/author/` | verified session or API key | The authors newest first. Query `q` (name or slug, accent and case insensitive), `page` (default 1), `size` (5, 25, 50 or 100, default 25). Body `{ items, total, page, size }`; a bad query is 400 with the body-mismatch message. |
| `POST /v1/author/` | owner or admin, session only | Create. 201 with the author. `user_id` links an account that has no author. |
| `POST /v1/author/me` | any verified session | Create the caller's own author from the display name (or the username). A taken slug gets `-2`, `-3`... silently. 201 with the author plus `slug_adjusted`: `true` when the stored slug differs from the plain slug of the name (a collision suffix was added), `false` otherwise. No other author response carries this field. |
| `PATCH /v1/author/{id}` | owner or admin on any author; any verified session on the author linked to it; session only | Edit `name`, `slug`, `bio`, `avatar_id`, `website`, `social_links`, `user_id`. Absent fields are untouched, `avatar_id`, `website` and `user_id` accept `null`, `social_links` is replaced as a whole. `user_id` links or unlinks the account and is owner or admin only. |
| `DELETE /v1/author/{id}?reassign_to={id\|none}` | owner or admin, session only | 204. An author credited on articles needs `reassign_to`: an author id (that author takes the deleted one's position and is never duplicated on an article) or `none` (the credit is removed). The move and the delete are one transaction. `reassign_to` is ignored when the author has no article. The linked account is untouched. |

The role checks use the existing bodies: 403 "Only owners and admins can do this." for `POST /` and
`DELETE`, 403 `author_rights` for a `PATCH` by an account that is not owner or admin on an author
that is not its own (or that sends `user_id`), and 403 "This action needs a real session." for a key.
Errors are plain text whose body is exactly the token: 404 `author_not_found`, 404 `user_not_found`,
409 `author_slug_taken`, 409 `author_has_articles`, 409 `user_already_linked`, 409
`author_already_linked`, 400 `invalid_slug`, 400 `invalid_reassign` (own id, not a whole number,
negative or empty), 400 `image_not_found`, 422 `bio_too_long`, 422 `invalid_url` and 422
`too_many_links`. A body that cannot be decoded, an empty `PATCH` or one that nulls a required field
is 400 with the body-mismatch message, a malformed id is 400 with the uint32 message and other
validation failures (`name`, link `type`) are 400 with the validator text. Writes refused for a
reason other than a missing target or an invalid value are recorded as failed events.

Articles carry `authors`, the ordered credits (the first is the primary byline), each with only `id`,
`name`, `slug`, `bio`, `avatar_id`, `website` and `social_links`; it is `[]` when there is none and it
is visible on online articles to anonymous readers. `PATCH /v1/article/{id}` also takes
`author_ids`, the whole ordered list: it replaces the credits, `[]` empties them, an unknown id is 404
`author_not_found`, a duplicate, `null` or a malformed list is 400 with the body-mismatch message and
`0` is 400 with the validator text. Absent means unchanged. A new article is credited to the
creator's linked author when there is one. `GET /v1/auth/me` returns the existing user fields plus
`author`: the caller's linked author (`id`, `name`, `slug`, `bio`, `avatar_id`, `website`,
`social_links`, `article_count`) or `null`.

An author's `avatar_id` counts as a use of that image like a site's social image: it raises `used_in`
and keeps the image out of the `unused` filter, and `GET /v1/media/{id}/usage` lists the author with the field `avatar`.
Deleting the image sets `avatar_id` to `null`. `POST /v1/media/merge` and `POST /v1/media/purge`
repoint the avatars of the merged copies and report it as `authors_updated`.

## Image variants
Owners and admins manage named variants of the stored images. These routes are session only (no API
key) and sit behind the verified-user check; any other role gets 403 "Only owners and admins can do
this." Behaviour, caching and the public `?v=<name>` contract are in [image-variants.md](image-variants.md).

| Route | Purpose |
| --- | --- |
| `GET /v1/image-variants` | `{ "items": [...] }`, ordered by name. |
| `POST /v1/image-variants` | Create. 201 with the variant. 409 when the name exists. |
| `PUT /v1/image-variants/{name}` | Replace the definition (the name in the body is ignored). 200 with the variant and `purged_files`. |
| `PATCH /v1/image-variants/{name}` | `{ "enabled": true }` or `{ "enabled": false }`. Keeps the generated files. |
| `DELETE /v1/image-variants/{name}` | 204. Removes the definition and its generated files. |
| `POST /v1/image-variants/{name}/purge` | `{ "purged_files", "purged_bytes" }`. Keeps the definition. |
| `GET /v1/image-variants/cache` | Cache statistics, see below. |
| `POST /v1/image-variants/cache/purge` | Purge generated files by scope, see below. |

A variant is `{ name, width, height, fit, format, quality, generate_on_upload, enabled,
generated_files, cache_size, created_at, updated_at }`. `width` and `height` are 1 to 8000 or `null`
(at least one is required), `fit` is `cover`, `contain` or `inside` (default `cover`), `format` is
`original`, `jpeg`, `png` or `webp` (default `original`), `quality` is 1 to 100 (default 82, `null`
for `png`), `generate_on_upload` defaults to `false`, `enabled` to `true`, and `cache_size` is in
bytes. A `PUT` that omits `generate_on_upload` or `enabled` keeps the stored value.

Errors are plain text: 400 for a body that is not valid JSON, 404 "Variant not found", 409 "A variant
named “thumb” already exists. Choose another name." and 422 with one sentence for the first invalid
field (name, width and height, fit, format, quality).

### Cache statistics and purge by scope

`GET /v1/image-variants/cache` answers `{ generated_files, disk_used, variants_defined,
variants_enabled, variants_disabled, rejected_requests, rejected_window_days, unused: { files, bytes,
days }, by_variant: [{ name, enabled, files, bytes }], top_images: [{ id, filename, url, files, bytes }] }`.
`by_variant` lists every defined variant by bytes descending then name; `top_images` lists the ten
images using the most variant bytes (ties by id, images that no longer exist are skipped). `unused`
counts the files of enabled variants whose reference time (the last public request, or the creation
time when never requested) is older than 30 days. `rejected_requests` counts the public requests
refused with 400 over today and the six previous UTC days. Pending request tracking is flushed before
the read. Arrays are never `null`.

`POST /v1/image-variants/cache/purge` takes `{ "scope": "all" | "unused" | "variant" | "image",
"variant": "<name>", "image_id": <id> }` (`variant` for the scope `variant`, `image_id` for `image`; a
target given for another scope is ignored) and answers `{ scope, purged_files, purged_bytes,
failed_files }`. A purge that fails on some files still answers 200 with `failed_files` above 0; the
failed rows are kept so the same request can be sent again. Errors are plain text: 400 for a body that
is not valid JSON, 422 "Scope must be all, unused, variant or image." or "A variant name or an image
id is required for this scope.", 404 "Variant not found" or "Image not found", 500 when the rows
cannot be listed.

### Variants of one image
Owners and admins only, session only: a request with an API key is 401. All ids are image ids.

| Route | Purpose |
| --- | --- |
| `GET /v1/media/{id}/variants` | `{ "unsupported": null, "items": [...] }` for the enabled variants in name order. `unsupported` is `"svg"` (with `items: []`) for an SVG. |
| `POST /v1/media/{id}/variants` | Generates every enabled variant that is missing. `{ "generated", "failed", "failures": [{ "name", "cause" }], "items": [...] }`, 200 even when some fail. |
| `POST /v1/media/{id}/variants/{name}` | Generates one enabled variant. 200 with the item. |
| `DELETE /v1/media/{id}/variants/{name}` | Removes the generated file. `{ "purged_files", "purged_bytes" }`, also for a disabled variant. |

An item is `{ name, width, height, fit, format, output_width, output_height, output_format,
generated, size, url }`: `width` and `height` are the settings (`null` when auto), `output_*` the
size and format the file has or will have (never above the source), `generated` is true only when
the file exists with the variant's current settings, `size` is its bytes or `null`, and `url` is
`/static/uploadedImages/<stored name>?v=<name>`. A `cause` is `too_large`, `unsupported_format` or
`failed`. A file generated here is the same file the public url serves, and the other way round.
Uploads generate the variants flagged `generate_on_upload` (enabled ones, raster sources only)
before answering; a failure there is logged and never fails the upload.

Errors are plain text: 400 for a malformed id, 404 "Image not found" or "Variant not found" (also for a
disabled variant on `POST`), 413 "The source image is too large to generate this variant.", 415 "The
source image can't be read, so this variant can't be generated.", 422 "Variants aren't generated for
this format." and 500 "Internal server error".

## Errors
Every error is a plain-text body with one sentence; the status is in the HTTP status line. The
statuses are 400, 401, 403, 404, 409, 429 and 500. Messages are listed on the Integration page.

## Notes
- Images in `body` use paths like `/static/uploadedImages/<uuid>.png`. Prefix them with the base URL.
- Browsers can call the API only from origins in the server's CORS setting.