docs: def get_user_identity(cls, instance_config):
          """
          Parse user identity out of init_config
  
          To guarantee a uniquely identifiable user, expects
          {"user": {"name": "my_username", "password": "my_password",
                    "domain": {"id": "my_domain_id"}
                    }
          }
          """
          user = instance_config.get('user')
  
          if not (
              user and user.get('name') and user.get('password') and user.get("domain") and user.get("domain").get("id")
          ):
              raise IncompleteIdentity()
  
          identity = {"methods": ['password'], "password": {"user": user}}
          return identity