feat: load explicit configuration references and remove implicit env overlays

examples/managedService/main.go

@@ -17,8 +17,15 @@ import (
 )
 
 func main() {
-	path := flag.String("config", "etc/config.yaml", "configuration file; empty uses defaults and environment")
+	path := flag.String("config", "etc/config.yaml", "configuration file; empty uses only Default()")
+	check := flag.Bool("check-config", false, "validate configuration and exit without starting dependencies")
 	flag.Parse()
+	if *check {
+		if _, err := config.Load(*path); err != nil {
+			log.Fatal(err)
+		}
+		return
+	}
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
 	if err := run(ctx, *path); err != nil {