Create a secure timed JWT token that can be passed. It save the user id,
        which later will be used to retrieve the data

        :param user: AuthUser, the user's object
        :param expires_in: - time in second for the token to expire
        :return: string

def create_jwt(self, expires_in=None):
        """
        Create a secure timed JWT token that can be passed. It save the user id,
        which later will be used to retrieve the data

        :param user: AuthUser, the user's object
        :param expires_in: - time in second for the token to expire
        :return: string
        """
        s = utils.sign_jwt(data={"id": self.user.id},
                           secret_key=get_jwt_secret(),
                           salt=get_jwt_salt(),
                           expires_in=expires_in or get_jwt_ttl())
        return s