Federate pinned statuses over ActivityPub (#6610)

* Federate pinned statuses over ActivityPub

* Display pinned toots in web UI

Fix #6117

* Fix migration

* Fix tests

* Update outbox_serializer.rb

* Update remove_serializer.rb

* Update add_serializer.rb

* Update fetch_featured_collection_service.rb

app/workers/activitypub/synchronize_featured_collection_worker.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class ActivityPub::SynchronizeFeaturedCollectionWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull'
+
+  def perform(account_id)
+    ActivityPub::FetchFeaturedCollectionService.new.call(Account.find(account_id))
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end