Implements command response framework

Adds interfaces and classes for a command response framework.

This change introduces `ICommandResponse` and associated classes to provide a standardized way of handling command execution results. It also updates the validation middleware to properly handle the new response types.

Removes an obsolete CommandResponse file.

Author: tomlazelle

sample/Domain/Commands/CreateWidget.cs

@@ -24,12 +24,8 @@ public async Task<CommandResponse<string>> Execute(CreateWidgetMessage message,
             response += $"Name: {message.Name} message was sent and processed with Success={eventargs.Success}";
         };
 
-        await _publisher.Publish(new WidgetCreated{Name = message.Name}, cancellationToken);
+        await _publisher.Publish(new WidgetCreated { Name = message.Name }, cancellationToken);
 
         return Response.Ok(response);
     }
-}
-
-public class V2
-{
 }

sample/Domain/Middleware/AsyncHandlerValidationMiddleware.cs

@@ -24,7 +24,7 @@ public async ValueTask InvokeAsync(
             context.ShouldContinue = false;
 
             // For CommandResponse, create an error response
-            if (typeof(TResponse) == typeof(CommandResponse))
+            if (typeof(TResponse) == typeof(ICommandResponse))
             {
                 context.Response = (TResponse)(object)new CommandResponse 
                 { 

src/CommandQuery.Framing/CommandResponse.cs

@@ -1,31 +1,82 @@
 using System;
+using System.Reflection.Metadata.Ecma335;
 
-namespace CommandQuery.Framing
+namespace CommandQuery.Framing;
+
+public interface ICommandResponse
+{
+    /// <summary>
+    /// Gets or sets a value indicating whether the operation was successful.
+    /// </summary>
+    bool Success { get; set; }
+
+    /// <summary>
+    /// Gets or sets a message describing the result (typically used for errors).
+    /// </summary>
+    string Message { get; set; }
+
+    /// <summary>
+    /// Gets or sets the exception that occurred, if any.
+    /// </summary>
+    Exception Exception { get; set; }
+
+    object RawData { get; }
+}
+
+/// <summary>
+/// Represents the response from executing a command or query.
+/// </summary>
+public class CommandResponse : ICommandResponse
+{
+    /// <summary>
+    /// Gets or sets a value indicating whether the operation was successful.
+    /// </summary>
+    public bool Success { get; set; }
+
+    /// <summary>
+    /// Gets or sets a message describing the result (typically used for errors).
+    /// </summary>
+    public string Message { get; set; }
+
+    /// <summary>
+    /// Gets or sets the exception that occurred, if any.
+    /// </summary>
+    public Exception Exception { get; set; }
+
+    public object RawData => null;
+}
+
+/// <summary>
+/// Represents the response from executing a command or query.
+/// </summary>
+/// <typeparam name="T">The type of data returned in the response.</typeparam>
+public class CommandResponse<T> : ICommandResponse
 {
     /// <summary>
-    /// Represents the response from executing a command or query.
+    /// Gets or sets a value indicating whether the operation was successful.
+    /// </summary>
+    public bool Success { get; set; }
+
+    /// <summary>
+    /// Gets or sets the response data.
     /// </summary>
-    /// <typeparam name="T">The type of data returned in the response.</typeparam>
-    public class CommandResponse<T>
+    private T _data;
+
+    public T Data
     {
-        /// <summary>
-        /// Gets or sets a value indicating whether the operation was successful.
-        /// </summary>
-        public bool Success { get; set; }
-
-        /// <summary>
-        /// Gets or sets the response data.
-        /// </summary>
-        public T Data { get; set; }
-
-        /// <summary>
-        /// Gets or sets a message describing the result (typically used for errors).
-        /// </summary>
-        public string Message { get; set; }
-        
-        /// <summary>
-        /// Gets or sets the exception that occurred, if any.
-        /// </summary>
-        public Exception Exception { get; set; }
+        get => _data;
+        set => _data = value;
     }
+
+    /// <summary>
+    /// Gets or sets a message describing the result (typically used for errors).
+    /// </summary>
+    public string Message { get; set; }
+
+    /// <summary>
+    /// Gets or sets the exception that occurred, if any.
+    /// </summary>
+    public Exception Exception { get; set; }
+
+    public object RawData => _data;
 }

test/CommandTests/DomainTests/CanGetMessageFromDomainPublisherTest.cs

@@ -1,7 +1,4 @@
-using System;
-using System.Threading;
-using System.Threading.Tasks;
-using CommandQuery.Framing;
+using CommandQuery.Framing;
 using Microsoft.Extensions.DependencyInjection;
 using Shouldly;
 
@@ -23,11 +20,17 @@ public async Task can_get_message_from_domain_publisher()
         var sentCnt = 0;
         var resultCnt = 0;
 
+        if (publisher is null)
+        {
+            throw new Exception("Publisher is null");
+        }
+
         publisher.MessageSent += (sender, args) => sentCnt++;
 
         publisher.MessageResult += (sender, args) => resultCnt++;
 
-        await publisher.Publish(new TestDomainEventMessage(), new CancellationToken());
+        var cancellationToken = CancellationToken.None;
+        await publisher.Publish(new TestDomainEventMessage(), cancellationToken);
 
         sentCnt.ShouldBe(2);
         resultCnt.ShouldBe(2);
@@ -40,11 +43,11 @@ public class TestDomainEventMessage
 
 public class TestDomainEvent : IDomainEvent<TestDomainEventMessage>
 {
-    public event EventHandler<DomainEventArgs> OnComplete;
+    public event EventHandler<DomainEventArgs>? OnComplete;
 
     public async Task Execute(TestDomainEventMessage message)
     {
-        OnComplete(this,
+        OnComplete?.Invoke(this,
             new DomainEventArgs
             {
                 Message = "Completed",
@@ -57,11 +60,11 @@ public async Task Execute(TestDomainEventMessage message)
 
 public class TestDomainEventTwo : IDomainEvent<TestDomainEventMessage>
 {
-    public event EventHandler<DomainEventArgs> OnComplete;
+    public event EventHandler<DomainEventArgs>? OnComplete;
 
     public async Task Execute(TestDomainEventMessage message)
     {
-        OnComplete(this,
+        OnComplete?.Invoke(this,
             new DomainEventArgs
             {
                 Message = "Completed",