fix: technical debts left by the Sites, Authors and SEO slices, plus backend support for the new Sites and Authors pagination

docs/release-notes.md

@@ -41,11 +41,16 @@ Articles and sites now store the data a website needs for search and sharing, an
 - `POST /v1/article/{id}/seo/check` evaluates an article without saving, with optional overrides, and reports the suggestions, the status and whether the slug is free.
 - `GET /v1/article/` items carry `seo_status` and `seo_suggestions`, and the new `seo` parameter filters on the status.
 - `GET /v1/site/{key}/sitemap` lists the published URLs of a site, paged, with the total in `X-Total-Count`, which is now exposed to browsers through CORS.
+- `GET /v1/article/` counts gain `suggestions`, the number of visible articles that still have SEO suggestions.
+- `GET /v1/site/` takes `q`, `page` and `size` and sends the number of matching sites in `X-Total-Count`; without `page` and `size` every site is still returned, as a JSON array.
+- `GET /v1/author/` also sends its total in `X-Total-Count`.
+- `GET /v1/media/{id}` reads one image, with the fields of a media list item; a missing image answers `404` and a malformed id `400`.
 
 ### Upgrading
 
 - The first start after the upgrade adds the new columns, gives every existing article a slug generated from its title (in id order within each site, with `-2`, `-3` on conflicts) and creates the unique `(site_id, slug)` index. Nothing else changes, and a second start changes nothing.
 - A deleted article now frees its slug.
+- The slug backfill writes in batches of 500 rows, so a large database is migrated without one long transaction, and a start that was interrupted resumes where it stopped.
 
 ## Published releases