feat: remove the 10,000-character article body limit and make the New article body optional

features/edit_article_body.feature

@@ -19,9 +19,9 @@ Feature: An authenticated user can edit an article's body
       DELETE /v1/article/{id}, PATCH /v1/article/{id}/publish and
       PATCH /v1/article/{id}/unpublish in api/router.go, so it also requires a valid
       jwt cookie
-    And the request body is JSON {"body": "..."}, validated with
-      validate:"required,max=10000" on the Body field, the same tag PostArticle.Body
-      already carries
+    And the request body is JSON {"body": "..."}; the Body field carries no validate tag
+      (no max, not required), as PostArticle.Body, per
+      features/article_body_unlimited.feature
     And a successful edit answers 200 with the JSON body of the updated article.Article,
       the same shape GetArticle, PostArticle, PublishArticle and UnpublishArticle
       already return; the article's title, is_online flag and images are unchanged
@@ -30,9 +30,8 @@ Feature: An authenticated user can edit an article's body
       PublishArticle and UnpublishArticle
     And a body that is not valid JSON answers 400 with body apperr.BodyErrorMessage,
       the same as PostArticle
-    And a body that fails its own required/max=10000 validation answers 400 with the
-      raw validator error text, the same as PostArticle already does for its own
-      fields; no new apperr message is introduced for this
+    And no body value fails validation: an empty or absent body and a body of any length
+      are accepted
     And an id absent from the article repository answers 404 with body
       apperr.ArticleNotFoundErrorMessage, backed by
       errors.Is(err, article.ErrArticleNotFound), the same as DeleteArticle,
@@ -84,11 +83,12 @@ Feature: An authenticated user can edit an article's body
     Then the response status is 400
     And the response body is the text apperr.BodyErrorMessage
 
-  Scenario Outline: A body value that fails validation answers 400
+  Scenario Outline: A body of any length, including empty, is accepted
     Given a valid jwt cookie for a user with id 1
     And the article repository contains an article with id 1
     When the client sends PATCH /v1/article/1 with that cookie and body <payload>
-    Then the response status is 400
+    Then the response status is 200
+    And the stored body equals the sent body
 
     Examples:
       | payload                              |