feat(discord): add opt-in mobile rich presence with track artwork

integration_test/discord_sdk_test.dart

@@ -0,0 +1,24 @@
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:integration_test/integration_test.dart';
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  testWidgets('native Discord SDK can initialize, stop, and restart', (
+    tester,
+  ) async {
+    const channel = MethodChannel('com.zarz.spotiflac/discord');
+    // Staging the official SDK is a prerequisite for this device-only test.
+    // No account is linked and no listening activity is published.
+    for (var i = 0; i < 2; i++) {
+      try {
+        expect(await channel.invokeMethod<bool>('initialize'), isTrue);
+        await tester.pump(const Duration(milliseconds: 350));
+        await channel.invokeMethod<void>('clear');
+      } finally {
+        await channel.invokeMethod<void>('shutdown');
+      }
+    }
+  });
+}