Added warning message for cmdlets in Az.Cdn (#17789)

* Adde warning message for cmdlets in Az.Cdn

* Add change log

* polish warning message

Author: BethanyZhou

src/Cdn/Cdn/ChangeLog.md

@@ -19,6 +19,7 @@
 -->
 
 ## Upcoming Release
+* Added breaking change messages for all cmdlets in Az.CDN module
 
 ## Version 1.8.2
 * Added breaking change messages for upcoming breaking change release of version 2.0.0

src/Cdn/Cdn/Common/AzureCdnCmdletBase.cs

@@ -14,6 +14,9 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
+
+using Microsoft.Azure.Commands.Cdn.Helpers;
 using Microsoft.Azure.Commands.Common.Authentication;
 using Microsoft.Azure.Commands.Common.Authentication.Abstractions;
 using Microsoft.Azure.Commands.ResourceManager.Common;
@@ -25,7 +28,6 @@ namespace Microsoft.Azure.Commands.Cdn.Common
     /// <summary>
     /// Base class of Azure Cdn Cmdlet.
     /// </summary>
-    [GenericBreakingChange("When you bump up Az.CDN module version, there will be changes to parameters and output, please use the new version", "2.0.0")]
     public class AzureCdnCmdletBase : AzureRMCmdlet
     {
         private ICdnManagementClient _cdnManagementClient;
@@ -79,5 +81,13 @@ public void ConfirmAction(bool force, string actionMessage, Action action)
                 action();
             }
         }
+
+        protected override void BeginProcessing()
+        {
+            CdnMessageHelper.WriteMessage(this,
+                $"Breaking changes in the cmdlet: { MyInvocation.InvocationName}" + Environment.NewLine +
+                "- When you bump up Az.CDN module version, there will be changes to parameters and output, please use the new version: 2.0.0");
+            base.BeginProcessing();
+        }
     }
 }

src/Cdn/Cdn/Helpers/CdnMessageHelper.cs

@@ -0,0 +1,25 @@
+using Microsoft.WindowsAzure.Commands.Common.CustomAttributes;
+
+using System;
+using System.Collections.Generic;
+using System.Management.Automation;
+using System.Text;
+
+namespace Microsoft.Azure.Commands.Cdn.Helpers
+{
+    internal static class CdnMessageHelper
+    {        
+        private const string SuppressEnvVar = BreakingChangeAttributeHelper.SUPPRESS_ERROR_OR_WARNING_MESSAGE_ENV_VARIABLE_NAME;
+       
+        private static bool IsMessageSuppressed =>
+            bool.TryParse(Environment.GetEnvironmentVariable(SuppressEnvVar), out bool result) && result;
+
+        internal static void WriteMessage(Cmdlet cmdlet, string message)
+        {
+            if (!IsMessageSuppressed)
+            {
+                cmdlet.WriteWarning(message);
+            }
+        }
+    }
+}