checker: build host FQDN from subdomain + apex at service scope

checker/collect.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	sdk "git.happydns.org/checker-sdk-go/checker"
+	happydns "git.happydns.org/happyDomain/model"
 	"golang.org/x/net/html"
 )
 
@@ -143,7 +144,22 @@ func buildTarget(ctx context.Context, opts sdk.CheckerOptions) (Target, error) {
 		userAgent = v
 	}
 
-	host, ips := addressesFromServer(server)
+	// Origin is the FQDN where the service is mounted: svc.Domain holds the
+	// subdomain (relative to apex; "@" for apex), and the domain_name
+	// autofill carries the zone apex.
+	apex := ""
+	if v, ok := sdk.GetOption[string](opts, OptionDomainName); ok {
+		apex = strings.TrimSuffix(v, ".")
+	}
+	subdomain := ""
+	if svc, ok := sdk.GetOption[happydns.ServiceMessage](opts, OptionService); ok {
+		subdomain = strings.TrimSuffix(svc.Domain, ".")
+	}
+	origin := sdk.JoinRelative(subdomain, apex)
+	host, ips := addressesFromServer(server, origin)
+	if host == "" {
+		host = origin
+	}
 	// abstract.Server only pins one A and one AAAA. Resolve the host to
 	// pick up any additional records the authoritative DNS exposes, so
 	// multi-IP deployments aren't silently under-probed. Failures are