Fetch reblogs as Announce activity instead of Note object (#4672)

* Process Create / Announce activity in FetchRemoteStatusService

* Use activity URL in ActivityPub for reblogs

* Redirect to the original status on StatusesController#show

app/serializers/activitypub/activity_serializer.rb

@@ -6,7 +6,7 @@ class ActivityPub::ActivitySerializer < ActiveModel::Serializer
   has_one :proper, key: :object, serializer: ActivityPub::NoteSerializer
 
   def id
-    [ActivityPub::TagManager.instance.uri_for(object), '/activity'].join
+    [ActivityPub::TagManager.instance.activity_uri_for(object)].join
   end
 
   def type