chore(demo): add clear all notifications button

Author: fadi-george

examples/demo/Assets/Scripts/Repositories/OneSignalRepository.cs

@@ -70,6 +70,8 @@ public void SendOutcomeWithValue(string name, float value) =>
 
         public void OptOutPush() => OneSignal.User.PushSubscription.OptOut();
 
+        public void ClearAllNotifications() => OneSignal.Notifications.ClearAllNotifications();
+
         public bool HasPermission() => OneSignal.Notifications.Permission;
 
         public Task<bool> RequestPermissionAsync(bool fallbackToSettings) =>

examples/demo/Assets/Scripts/UI/Sections/SendPushSectionController.cs

@@ -53,6 +53,14 @@ private VisualElement BuildSection()
                 )
             );
 
+            section.Add(
+                SectionBuilder.CreateDestructiveButton(
+                    "CLEAR ALL",
+                    "clear_all_notifications",
+                    () => _viewModel.ClearAllNotifications()
+                )
+            );
+
             return section;
         }
     }

examples/demo/Assets/Scripts/ViewModels/AppViewModel.cs

@@ -338,6 +338,13 @@ public async void SendNotification(NotificationType type)
             }
         }
 
+        public void ClearAllNotifications()
+        {
+            _repository.ClearAllNotifications();
+            LogManager.Instance.Info(Tag, "All notifications cleared");
+            ShowToast("All notifications cleared");
+        }
+
         public async void SendCustomNotification(string title, string body)
         {
             try