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

Conflicts:
- `app/views/admin/settings/appearance/show.html.haml`:
  Upstream enforced an uniform code style around lambdas, and glitch-soc
  had a different lambda due to its theming system.
  Applied the same code style changes.
- `app/views/settings/preferences/appearance/show.html.haml`:
  Upstream enforced an uniform code style around lambdas, and glitch-soc
  removed some code just after the lambda.
  Applied the same code style changes.

app/services/activitypub/process_collection_service.rb

@@ -8,6 +8,8 @@ class ActivityPub::ProcessCollectionService < BaseService
     @json    = original_json = Oj.load(body, mode: :strict)
     @options = options
 
+    return unless @json.is_a?(Hash)
+
     begin
       @json = compact(@json) if @json['signature'].is_a?(Hash)
     rescue JSON::LD::JsonLdError => e