Revert "Changes to this file no longer needed"

This reverts commit 2c6c3ac6a4.

Source/MQTTnet.Extensions.ManagedClient/ManagedMqttApplicationMessage.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace MQTTnet.Extensions.ManagedClient
+{
+    public class ManagedMqttApplicationMessage : IEquatable<ManagedMqttApplicationMessage>
+    {
+        public Guid Id { get; set; } = Guid.NewGuid();
+
+        public MqttApplicationMessage ApplicationMessage { get; set; }
+       
+        public bool Equals(ManagedMqttApplicationMessage other)
+        {
+            return Id.Equals(other.Id);
+        }
+    }
+}