pub fn normalize_host(host: &str) -> Result<String>Expand description
Normalizes and validates a hostname exactly like normalize_domain, but
keeps a leading www. label.
For operations about one specific DNS name rather than its registration:
record lookups (dig www.example.com CNAME must query www, not the
apex), propagation/follow/compare, and per-host probes such as takeover
detection, where www is the single most commonly CNAME’d host.