FEATURE: add site setting to include user associated account ids. (#18375)

By default, we won't include associated account ids in current user serializer. If the new hidden site setting `include_associated_account_ids` is enabled then we will add it in the serializer.

config/site_settings.yml

@@ -2018,6 +2018,9 @@ developer:
     default: ""
     allow_any: false
     refresh: true
+  include_associated_account_ids:
+    default: false
+    hidden: true
 
 embedding:
   embed_by_username: