private function setCacheLifetime(Response $response)
    {
        $response->headers->set(
            SuluHttpCache::HEADER_REVERSE_PROXY_TTL,
            $response->getAge() + $this->container->getParameter('sulu_website.sitemap.cache.lifetime')
        );

        return $response->setMaxAge(240)
            ->setSharedMaxAge(960);
    }