private function appendCustomUrls(Webspace $webspace, Context $context, JsonSerializationVisitor $visitor)
    {
        $customUrls = [];
        foreach ($webspace->getPortals() as $portal) {
            $customUrls = array_merge(
                $customUrls,
                $this->getCustomUrlsForEnvironment($portal, $portal->getEnvironment($this->environment), $context)
            );
        }

        $customUrls = $context->accept($customUrls);
        $visitor->addData('customUrls', $customUrls);
    }