implement message subscribing and worker

dotnet/AipsCore/Application/Abstract/MessageBroking/IMessage.cs

@@ -0,0 +1,3 @@
+namespace AipsCore.Application.Abstract.MessageBroking;
+
+public interface IMessage;

dotnet/AipsCore/Application/Abstract/MessageBroking/IMessageHandler.cs

@@ -0,0 +1,6 @@
+namespace AipsCore.Application.Abstract.MessageBroking;
+
+public interface IMessageHandler<TMessage> where TMessage : IMessage
+{
+    Task Handle(TMessage message, CancellationToken cancellationToken);
+}

dotnet/AipsCore/Application/Abstract/MessageBroking/IMessageSubscriber.cs

@@ -0,0 +1,8 @@
+namespace AipsCore.Application.Abstract.MessageBroking;
+
+public interface IMessageSubscriber
+{
+    Task SubscribeAsync<T>(
+        Func<T, CancellationToken, Task> handler
+    );
+}

dotnet/AipsCore/Application/Abstract/MessageBroking/MessageTag.cs

@@ -0,0 +1,7 @@
+namespace AipsCore.Application.Abstract.MessageBroking;
+
+public enum MessageTag
+{
+    Worker,
+    RT
+}