Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `app/javascript/mastodon/features/compose/components/compose_form.js`:
  Conflict caused because of minor code style change upstream, while glitch-soc
  has different code for handling variable maximum chars.
  Ported the change.
- `app/serializers/initial_state_serializer.rb`:
  Conflict because glitch-soc had two extra attributes where upstream added
  one.
  Added upstream's attribute.

app/serializers/rest/preferences_serializer.rb

@@ -17,7 +17,7 @@ class REST::PreferencesSerializer < ActiveModel::Serializer
   end
 
   def posting_default_language
-    object.user.setting_default_language.presence
+    object.user.preferred_posting_language
   end
 
   def reading_default_sensitive_media