Members API: Allow adding member by Username
case of 'Add a member to a group or project ' rest api
Could you allow username as well as user_id in parameter user_id?
Add a member to a group or project
GET /groups/:id/members GET /projects/:id/members
|user_id||integer||yes||The user ID of the new member|
|user_id||integer/string||yes||The user ID or username of the new member|