Implement new managed client.

Source/MQTTnet.Extensions.ManagedClient/New/MaintainConnectionResult.cs

@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace MQTTnet.Extensions.ManagedClient
+{
+    public enum MaintainConnectionResult
+    {
+        NoChange,
+
+        ConnectedEstablished,
+
+        NotConnected
+    }
+}