code: func NameIsDNSSubdomain(name string, prefix bool) (bool, string) {
  	if prefix {
  		name = maskTrailingDash(name)
  	}
  	if validation.IsDNS1123Subdomain(name) {
  		return true, ""
  	}
  	return false, DNSSubdomainErrorMsg
  }
docs: // NameIsDNSSubdomain is a ValidateNameFunc for names that must be a DNS subdomain.