Add data model.

src/DotNetCore.CAP/MessageData.cs

+using System;
+using DotNetCore.CAP.Models;
+
+namespace DotNetCore.CAP
+{
+    public class MessageData
+    {
+        public string State { get; set; }
+        public Message Message { get; set; }
+        public DateTime CreatedAt { get; set; }       
+    }
+}
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src/DotNetCore.CAP/StateData.cs

+using System.Collections.Generic;
+
+namespace DotNetCore.CAP
+{
+    public class StateData
+    {
+        public string Name { get; set; }
+
+        public string Reason { get; set; }
+
+        public IDictionary<string, string> Data { get; set; } 
+    }
+}
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