fix: preserve live Nginx entry when saved draft differs

backend/internal/nginxgateway/gateway_test.go

@@ -3,8 +3,30 @@ package nginxgateway
 import (
 	"errors"
 	"testing"
+
+	"vpn-platform/backend/internal/nginxconfig"
 )
 
+func TestParseManagedEntry(t *testing.T) {
+	for _, want := range []nginxconfig.RenderOptions{
+		{Domain: "vpn.example.com", Scheme: "https", Port: 443},
+		{Domain: "vpn.example.com", Scheme: "https", Port: 8443},
+		{Domain: "vpn.example.com", Scheme: "http", Port: 28080},
+	} {
+		httpSite, httpsSite, err := nginxconfig.RenderWithOptions(want, nil, 0)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := parseManagedEntry(httpSite + httpsSite)
+		if err != nil || got != want {
+			t.Fatalf("parse managed entry = %+v, %v; want %+v", got, err, want)
+		}
+	}
+	if _, err := parseManagedEntry("server { listen 443 ssl; }"); err == nil {
+		t.Fatal("unmanaged site must be rejected")
+	}
+}
+
 func TestSwapManagedSiteRestoresPreviousOnFailure(t *testing.T) {
 	for _, failAt := range []string{"validate", "reload", "persist"} {
 		t.Run(failAt, func(t *testing.T) {