Add package in_app_purchase (not implemented - but otherwise google-play wont verify)

flutter/lib/main.dart

@@ -1,8 +1,10 @@
+import 'dart:async';
 import 'dart:io';
 
 import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
+import 'package:in_app_purchase/in_app_purchase.dart';
 import 'package:provider/provider.dart';
 import 'package:simplecloudnotifier/main_messaging.dart';
 import 'package:simplecloudnotifier/main_utils.dart';
@@ -151,11 +153,48 @@ void main() async {
   );
 }
 
-class SCNApp extends StatelessWidget {
+class SCNApp extends StatefulWidget {
   SCNApp({super.key});
 
   static var materialKey = GlobalKey<NavigatorState>();
 
+  @override
+  State<SCNApp> createState() => _SCNAppState();
+}
+
+class _SCNAppState extends State<SCNApp> {
+  StreamSubscription<List<PurchaseDetails>>? _purchaseSubscription;
+
+  @override
+  void initState() {
+    _purchaseSubscription = InAppPurchase.instance.purchaseStream.listen(
+      purchaseUpdated,
+      onDone: () => _purchaseSubscription?.cancel(),
+      onError: purchaseError,
+    );
+    super.initState();
+  }
+
+  @override
+  void dispose() {
+    _purchaseSubscription?.cancel();
+    _purchaseSubscription = null;
+    super.dispose();
+  }
+
+  void purchaseUpdated(List<PurchaseDetails> purchaseDetailsList) {
+    // see https://pub.dev/packages/in_app_purchase
+
+    for (var purchaseDetails in purchaseDetailsList) {
+      ApplicationLog.debug('Purchase ${purchaseDetails.productID} is ${purchaseDetails.status.toString()}'); //TODO
+    }
+  }
+
+  void purchaseError(dynamic error) {
+    // TODO handle error here.
+    ApplicationLog.error('Purchase error: ${error.toString()}', trace: StackTrace.current);
+  }
+
   @override
   Widget build(BuildContext context) {
     return ToastificationWrapper(