FEATURE: User fields required for existing users - Part 2 (#27172)

We want to allow admins to make new required fields apply to existing users. In order for this to work we need to have a way to make those users fill up the fields on their next page load. This is very similar to how adding a 2FA requirement post-fact works. Users will be redirected to a page where they can fill up the remaining required fields, and until they do that they won't be able to do anything else.

app/serializers/current_user_serializer.rb

@@ -58,6 +58,7 @@ class CurrentUserSerializer < BasicUserSerializer
              :associated_account_ids,
              :top_category_ids,
              :groups,
+             :needs_required_fields_check?,
              :second_factor_enabled,
              :ignored_users,
              :featured_topic,