fix: missing messageId serialization

Author: VisualBean

src/ByteBard.AsyncAPI/Models/AsyncApiMessage.cs

@@ -99,6 +99,7 @@ public virtual void SerializeV2(IAsyncApiWriter writer)
             }
 
             writer.WriteStartObject();
+            writer.WriteOptionalProperty(AsyncApiConstants.MessageId, this.MessageId);
             writer.WriteOptionalObject(AsyncApiConstants.Headers, this.Headers, (w, h) => h.SerializeV2(w));
             writer.WriteOptionalObject(AsyncApiConstants.Payload, this.Payload, (w, p) => p.SerializeV2(w));
             writer.WriteOptionalObject(AsyncApiConstants.CorrelationId, this.CorrelationId, (w, c) => c.SerializeV2(w));
@@ -119,4 +120,4 @@ public virtual void SerializeV2(IAsyncApiWriter writer)
             writer.WriteEndObject();
         }
     }
-}
+}

test/ByteBard.AsyncAPI.Tests/Models/AsyncApiMessage_Should.cs

@@ -243,6 +243,7 @@ public void AsyncApiMessage_WithFilledObject_Serializes()
         {
             var expected =
                 """
+                messageId: myMessage
                 headers:
                   title: HeaderTitle
                   description: HeaderDescription
@@ -313,6 +314,7 @@ public void AsyncApiMessage_WithFilledObject_Serializes()
 
             var message = new AsyncApiMessage
             {
+				MessageId = "myMessage",
                 Headers = new AsyncApiJsonSchema
                 {
                     Title = "HeaderTitle",