fix: write generated Caddyfile to disk only if succesfully loaded into local Caddy (means valid)

internal/machine/caddyconfig/caddyfile.go

@@ -54,6 +54,9 @@ https://{{$hostname}} {
 	}
 	log
 }{{end}}
+`
+	caddyfileUnavailabeFooter = `# NOTE: User-defined configs for services were skipped because Caddy is not running on this machine
+#       or the latest generated config is invalid. Please check the Caddy logs if it's running.
 `
 )
 
@@ -118,9 +121,7 @@ func (g *CaddyfileGenerator) Generate(
 	}
 
 	if !includeCustom {
-		return fmt.Sprintf("%s\n%s\n"+
-			"# NOTE: User-defined configs for services were skipped because Caddy is not running on this machine.\n",
-			caddyfileHeader, caddyfile), nil
+		return fmt.Sprintf("%s\n%s\n%s", caddyfileHeader, caddyfile, caddyfileUnavailabeFooter), nil
 	}
 
 	upstreams := serviceUpstreams(containers)