public function getHttpRedirectBindingResponse(AuthnRequest $request = null)
    {
        if (is_null($request)) {
            $request = $this->buildAuthnRequest();
        }

        $context = new MessageContext();
        $context->setMessage($request);

        $binding = (new BindingFactory())->create(SamlConstants::BINDING_SAML2_HTTP_REDIRECT);

        return new RedirectResponse($binding->send($context)->getTargetUrl());
    }