fix(datastore): Clear subscriptions on Stop (#5253)

Author: Equartey

packages/amplify_datastore/android/src/main/kotlin/com/amazonaws/amplify/amplify_datastore/pigeons/NativePluginBindings.kt

@@ -234,6 +234,9 @@ public class SwiftAmplifyDataStorePlugin: NSObject, FlutterPlugin, NativeAmplify
             onStart(flutterResult: result)
         case "stop":
             onStop(flutterResult: result)
+            DispatchQueue.main.async {
+                self.nativeApiPlugin.onStop {}
+            }
         default:
             result(FlutterMethodNotImplemented)
         }

packages/amplify_datastore/ios/Classes/SwiftAmplifyDataStorePlugin.swift

@@ -375,4 +375,14 @@ class NativeAmplifyApi
       _subscriptionsCache.remove(subscriptionId);
     }
   }
+
+  /// Amplify.DataStore.Stop() callback
+  ///
+  /// Clean up subscriptions on stop.
+  @override
+  Future<void> onStop() async {
+    _subscriptionsCache.forEach((subId, _) async {
+      await unsubscribe(subId);
+    });
+  }
 }

packages/amplify_datastore/ios/Classes/pigeons/NativePluginBindings.swift

@@ -41,6 +41,9 @@ abstract class NativeApiPlugin {
 
   @async
   void unsubscribe(String subscriptionId);
+
+  @async
+  void onStop();
 }
 
 /// Bridge for calling Amplify from Flutter into Native