Groups users
Users who are in a group.

GET /v2/groups_users
Return all the groups users

GET /v2/groups/:group_id/groups_users
Return all the groups users of the given Group

GET /v2/users/:user_id/groups_users
Return all the groups users of the given User

GET /v2/groups_users/:id
Get a groups user

POST /v2/groups_users
Create a groups user

PATCH /v2/groups_users/:id
Update a groups user

PUT /v2/groups_users/:id
Update a groups user

DELETE /v2/groups_users/:id
Destroy a groups user