added domain events, fix IQueryalbeProvider abstraction, added support for sagas and RabbitMQ

Svrnty.CQRS.Notifications.Abstractions/StreamingNotificationAttribute.cs

@@ -0,0 +1,15 @@
+namespace Svrnty.CQRS.Notifications.Abstractions;
+
+/// <summary>
+/// Marks a record as a streaming notification that can be subscribed to via gRPC.
+/// The framework will auto-generate proto definitions and service implementations.
+/// </summary>
+[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
+public sealed class StreamingNotificationAttribute : Attribute
+{
+    /// <summary>
+    /// The property name used as the subscription key.
+    /// Subscribers filter notifications by this value.
+    /// </summary>
+    public required string SubscriptionKey { get; set; }
+}