Improve federated ID validation (#8372)

* Fix URI not being sufficiently validated with prefetched JSON

* Add additional id validation to OStatus documents, when possible

app/services/activitypub/fetch_remote_account_service.rb

@@ -11,7 +11,7 @@ class ActivityPub::FetchRemoteAccountService < BaseService
     @json = if prefetched_body.nil?
               fetch_resource(uri, id)
             else
-              body_to_json(prefetched_body)
+              body_to_json(prefetched_body, compare_id: id ? uri : nil)
             end
 
     return if !supported_context? || !expected_type? || (break_on_redirect && @json['movedTo'].present?)