servesHost method
true when the folder serves host (the Host header). The domain
may have a port (localhost:3000) or not, like a domain route.
Implementation
bool servesHost(String? host) {
String? want = domain;
if (want == null) return true;
if (host == null) return false;
host = host.toLowerCase();
if (want == host) return true;
int end = host.startsWith('[') ? host.indexOf(']') + 1 : 0;
int colon = host.indexOf(':', end);
return colon != -1 && want == host.substring(0, colon);
}