fixup! feat!: improve TD serialization behavior

lib/src/binding_mqtt/mqtt_extensions.dart

@@ -145,7 +145,8 @@ extension MqttFormExtension on AugmentedForm {
     if (qosValue != null) {
       throw ValidationException(
         "Encountered unknown QoS value $qosValue. "
-        "in form with href $href",
+        "in form with href $href of Thing Description with Identifier "
+        "$tdIdentifier.",
       );
     }
 

test/binding_mqtt/mqtt_extension_test.dart

@@ -0,0 +1,60 @@
+// Copyright 2024 Contributors to the Eclipse Foundation. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+import "package:dart_wot/dart_wot.dart";
+import 'package:dart_wot/src/binding_mqtt/mqtt_extensions.dart';
+import "package:dart_wot/src/definitions/validation/validation_exception.dart";
+import "package:test/test.dart";
+
+void main() {
+  group("MQTT Binding Extensions should", () {
+    test("reject forms with unknown QoS values", () {
+      const id = "urn:foobar";
+      const href = "mqtt://example.org/test";
+      final thingDescription = ThingDescription.fromJson(
+        const {
+          "@context": [
+            "https://www.w3.org/2022/wot/td/v1.1",
+            {
+              "mqv": "http://www.example.org/mqtt-binding#",
+            }
+          ],
+          "title": "Test TD",
+          "id": id,
+          "properties": {
+            "test": {
+              "forms": [
+                {
+                  "href": href,
+                  "mqv:qos": "foobar",
+                }
+              ],
+            },
+          },
+          "security": ["nosec_sc"],
+          "securityDefinitions": {
+            "nosec_sc": {
+              "scheme": "nosec",
+            },
+          },
+        },
+      );
+      final affordance = thingDescription.properties?["test"];
+
+      final augmentedForm = AugmentedForm(
+        affordance!.forms.first,
+        affordance,
+        thingDescription,
+        const {},
+      );
+
+      expect(
+        () => augmentedForm.qualityOfService,
+        throwsA(isA<ValidationException>()),
+      );
+    });
+  });
+}