public function addCommand($siteNodeName, $hostname, $scheme = null, $port = null)
    {
        $site = $this->siteRepository->findOneByNodeName($siteNodeName);
        if (!$site instanceof Site) {
            $this->outputLine('<error>No site found with nodeName "%s".</error>', [$siteNodeName]);
            $this->quit(1);
        }

        $domains = $this->domainRepository->findByHostname($hostname);
        if ($domains->count() > 0) {
            $this->outputLine('<error>The host name "%s" is not unique.</error>', [$hostname]);
            $this->quit(1);
        }

        $domain = new Domain();
        if ($scheme !== null) {
            $domain->setScheme($scheme);
        }
        if ($port !== null) {
            $domain->setPort($port);
        }
        $domain->setSite($site);
        $domain->setHostname($hostname);

        $domainValidator = $this->validatorResolver->getBaseValidatorConjunction(Domain::class);
        $result = $domainValidator->validate($domain);
        if ($result->hasErrors()) {
            foreach ($result->getFlattenedErrors() as $propertyName => $errors) {
                $firstError = array_pop($errors);
                $this->outputLine('<error>Validation failed for "' . $propertyName . '": ' . $firstError . '</error>');
                $this->quit(1);
            }
        }

        $this->domainRepository->add($domain);

        $this->outputLine('Domain entry created.');
    }