N+1 Query in namespaces api

The Namespaces API has a N+1 query problem as discussed here !22121 (comment 264034946)

TESTING

The test code is in the MR

THE N+1 queries

The N+1 queries in the namespace API stem from the 3 fields exposed using the Grape API builder. It seems very easy to make N+1 mistakes, due to the way fields are exposed in Grape. More APIs might risk having N+1 query problems. The fix for all 3 will require some thinking, if at all practical. The MR currently includes just the failed N+1 spec.

1. billable_members_count = namespace.billable_members_count(options[:requested_hosted_plan])
2. full_path or web_url in the Routable concern
3. members_count_with_descendants = namespace.users_with_descendants.count