[GraphQL](http://graphql.org/learn/best-practices/) and deprecate the use of
controller-specific endpoints. GraphQL has a number of benefits:
1. We avoid having to maintain two different APIs.
2. Callers of the API can request only what they need.
3. It is versioned by default.
It will co-exist with the current v4 REST API. If we have a v5 API, this should
be a compatibility layer on top of GraphQL.
We have changed our plans to move to GraphQL. After reviewing the GraphQL license, anything related to the Facebook BSD plus patent license will not be allowed at GitLab.
