Add method to list the groups for a defined user
from the identity endpoint `/user/{user_id}/groups`
Change-Id: I32ef1634081e8194137fde3f8691650019892241
Add method to list the groups for a defined user
from the identity endpoint `/user/{user_id}/groups`
Change-Id: I32ef1634081e8194137fde3f8691650019892241