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

Conflicts:
- `app/models/account.rb`:
  Not a real conflict, just upstream getting rid of unused constants too close
  to glitch-soc-specific contents.
  Removed unused constants like upstream did.
- `app/models/trends.rb`:
  Conflict because glitch-soc disabled email notifications for trending links.
  Upstream has refactored this quite a bit and added trending posts.
  Took upstream code, but disabling the extra trending stuff will come in
  another commit.
- `app/views/admin/trends/links/index.html.haml`:
  Conflict due to glitch-soc's theming system.
  Ported upstream changes accordingly.

app/models/status.rb

@@ -27,6 +27,7 @@
 #  content_type           :string
 #  deleted_at             :datetime
 #  edited_at              :datetime
+#  trendable              :boolean
 #
 
 class Status < ApplicationRecord
@@ -274,6 +275,18 @@ class Status < ApplicationRecord
     update_status_stat!(key => [public_send(key) - 1, 0].max)
   end
 
+  def trendable?
+    if attributes['trendable'].nil?
+      account.trendable?
+    else
+      attributes['trendable']
+    end
+  end
+
+  def requires_review_notification?
+    attributes['trendable'].nil? && account.requires_review_notification?
+  end
+
   after_create_commit  :increment_counter_caches
   after_destroy_commit :decrement_counter_caches