Add support for editing media description and focus point of already-posted statuses (#20878)

* Add backend support for editing media attachments of existing posts

* Allow editing media attachments of already-posted toots

* Add tests

app/controllers/api/v1/statuses_controller.rb

@@ -79,6 +79,7 @@ class Api::V1::StatusesController < Api::BaseController
       current_account.id,
       text: status_params[:status],
       media_ids: status_params[:media_ids],
+      media_attributes: status_params[:media_attributes],
       sensitive: status_params[:sensitive],
       language: status_params[:language],
       spoiler_text: status_params[:spoiler_text],
@@ -128,6 +129,12 @@ class Api::V1::StatusesController < Api::BaseController
       :language,
       :scheduled_at,
       media_ids: [],
+      media_attributes: [
+        :id,
+        :thumbnail,
+        :description,
+        :focus,
+      ],
       poll: [
         :multiple,
         :hide_totals,