fillSetupUrls function
Implementation
SetupConfig fillSetupUrls(SetupConfig cfg) {
final region = _gatewayRegion(cfg.siteUrl) ?? _gatewayRegion(cfg.upgradeUrl);
if (region == null) return cfg;
final (site, upgrade) = _pairUrls(region);
if (cfg.siteUrl.isEmpty) cfg.siteUrl = site;
if (cfg.upgradeUrl.isEmpty) cfg.upgradeUrl = upgrade;
return cfg;
}