GET /user/groups/5/12/users
or
GET /user/group/5/12/users?limit=10&offset=0
Accept: application/vnd.ez.api.UserList+json

    {
       "UserList":
       {
           "_media-type": "application/vnd.ez.api.UserList+json",
           "_href": "/api/ezp/v2/user/groups/5/12/users",
           "User":
           [
           ]
       }
    }