Fix federation of avatars and images with legacy gab:// URLs

app/serializers/activitypub/gab_image_serializer.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class ActivityPub::GabImageSerializer < ActivityPub::ImageSerializer
+  def url
+    object
+      .sub('gab://avatar/', 'https://gab.com/media/user/')
+      .sub('gab://header/', 'https://gab.com/media/user/')
+  end
+
+  def media_type; end
+end