protected function prepareLinkHeader()
    {
        $links = new LinkHeader(array());
        $links->add(
            new LinkHeaderItem(
                $this->router->generate('graviton.core.rest.app.all', array (), UrlGeneratorInterface::ABSOLUTE_URL),
                array ('rel' => 'apps', 'type' => 'application/json')
            )
        );

        return (string) $links;
    }