feat(sample): add open-generic INotificationHandler<TNotification> demo

Agent-Logs-Url: https://github.com/hasanxdev/DispatchR/sessions/9ef271ed-cd29-415a-a675-f6a2be488540

Co-authored-by: hasanxdev <30981174+hasanxdev@users.noreply.github.com>

Author: Copilot

src/Sample/DispatchR/Notification/AllNotificationsLogger.cs

@@ -0,0 +1,19 @@
+using DispatchR.Abstractions.Notification;
+
+namespace Sample.DispatchR.Notification;
+
+/// <summary>
+/// Open-generic notification handler — handles every INotification published through DispatchR.
+/// Useful for cross-cutting concerns such as logging, auditing or telemetry.
+/// </summary>
+public sealed class AllNotificationsLogger<TNotification>(ILogger<AllNotificationsLogger<TNotification>> logger)
+    : INotificationHandler<TNotification>
+    where TNotification : INotification
+{
+    public ValueTask Handle(TNotification notification, CancellationToken cancellationToken)
+    {
+        logger.LogInformation("[Generic] Received notification of type {NotificationType}: {@Notification}",
+            typeof(TNotification).Name, notification);
+        return ValueTask.CompletedTask;
+    }
+}

src/Sample/DispatchR/Notification/GenericAwareNotification.cs

@@ -0,0 +1,5 @@
+using DispatchR.Abstractions.Notification;
+
+namespace Sample.DispatchR.Notification;
+
+public sealed record GenericAwareNotification(Guid Id, string Message) : INotification;

src/Sample/Program.cs

@@ -124,6 +124,16 @@
     return "It works";
 });
 
+// Demonstrates open-generic INotificationHandler<TNotification>:
+// AllNotificationsLogger<TNotification> is registered once and handles every INotification.
+// GenericAwareNotification is handled by both its own specific handler (if any) and the generic one.
+app.MapGet("/Notification/DispatchR/Generic", async (DispatchR.IMediator mediator, ILogger<Program> logger) =>
+{
+    var notification = new DispatchRNotificationSample.GenericAwareNotification(Guid.NewGuid(), "Hello from open-generic handler!");
+    await mediator.Publish(notification, CancellationToken.None);
+    return "It works";
+});
+
 app.Run();
 
 namespace Sample