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"}
                  }
        }

def _get_user_identity(user):
        """
        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"}
                  }
        }
        """
        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