protected function getUnauthorizedResponse()
    {
        $authHeaderValue = $this->realm === null ? static::AUTHENTICATION_SCHEME :
            static::AUTHENTICATION_SCHEME . ' realm="' . $this->realm . '"';

        return $this->integration->createResponse(
            null,
            Response::HTTP_UNAUTHORIZED,
            [self::HEADER_WWW_AUTHENTICATE => $authHeaderValue]
        );
    }