Decorates the authentication callback endpoint. The endpoint should
        take one argument, a flask.ext.micropub.AuthResponse.

def authenticated_handler(self, f):
        """Decorates the authentication callback endpoint. The endpoint should
        take one argument, a flask.ext.micropub.AuthResponse.
        """
        @functools.wraps(f)
        def decorated():
            resp = self._handle_authenticate_response()
            return f(resp)
        self._authenticated_handler = decorated
        return decorated