Handle an authentication request and pass it on to the backend.
        :type context: satosa.context.Context
        :rtype: oic.utils.http_util.Response

        :param context: the current context
        :return: HTTP response to the client

def handle_authn_request(self, context):
        """
        Handle an authentication request and pass it on to the backend.
        :type context: satosa.context.Context
        :rtype: oic.utils.http_util.Response

        :param context: the current context
        :return: HTTP response to the client
        """
        internal_req = self._handle_authn_request(context)
        if not isinstance(internal_req, InternalData):
            return internal_req
        return self.auth_req_callback_func(context, internal_req)