Fixes: Azure#15005: Set-AzAppServicePlan to keep existing Tags when adding new Tags (Azure#17650)

* Fix Azure#17184 :  `Get-AzWebApp` to return SiteConfig details in the response when requested the WebApps under subscreption

* Revert "Fix Azure#17184 :  `Get-AzWebApp` to return SiteConfig details in the response when requested the WebApps under subscreption"

This reverts commit 96a4d28.

* Fix Azure#17184 :  `Get-AzWebApp` to return SiteConfig details in the response when requested the WebApps under subscreption

* Revert "Fix Azure#17184 :  `Get-AzWebApp` to return SiteConfig details in the response when requested the WebApps under subscreption"

This reverts commit 96a4d28.

* Fixed Set-AzAppServicePlan to keep existing Tags when adding new Tags

Author: Kotasudhakarreddy

src/Websites/Websites.Test/SessionRecords/Microsoft.Azure.Commands.Websites.Test.ScenarioTests.AppServicePlanTests/TestCreateNewAppServicePlan.json

@@ -18,6 +18,7 @@
         - Additional information about change #1
 -->
 ## Upcoming Release
+* Fixed `Set-AzAppServicePlan` to keep existing Tags when adding new Tags 
 * Fixed `Set-AzWebApp`,`Set-AzWebAppSlot`, `Get-AzWebApp` and `Get-AzWebAppSlot` to expose `VnetRouteAllEnabled` property in `SiteConfig` [#15663]
 * Fixed `Set-AzWebApp`, `Set-AzWebAppSlot`, `Get-AzWebApp` and `Get-AzWebAppSlot` to expose `HealthCheckPath` property in `SiteConfig` [#16325]
 * Fixed DateTime conversion issue caused by culture [#17253]

src/Websites/Websites.Test/SessionRecords/Microsoft.Azure.Commands.Websites.Test.ScenarioTests.AppServicePlanTests/TestSetAppServicePlan.json

@@ -65,10 +65,20 @@ public override void ExecuteCmdlet()
                     int workerSizeAsNumber = 0;
                     int.TryParse(Regex.Match(AppServicePlan.Sku.Name, @"\d+").Value, out workerSizeAsNumber);
                     AppServicePlan.Sku.Name = string.IsNullOrWhiteSpace(WorkerSize) ? CmdletHelpers.GetSkuName(AppServicePlan.Sku.Tier, workerSizeAsNumber) : CmdletHelpers.GetSkuName(AppServicePlan.Sku.Tier, WorkerSize);
-                    AppServicePlan.PerSiteScaling = PerSiteScaling;                    
-                    if (Tag != null && AppServicePlan.Tags!=null)
-                        CmdletHelpers.ConvertToStringDictionary(Tag).ForEach(item => AppServicePlan.Tags?.Add(item));
-                    else
+                    AppServicePlan.PerSiteScaling = PerSiteScaling;
+                    if (Tag != null && AppServicePlan.Tags != null)
+                        CmdletHelpers.ConvertToStringDictionary(Tag).ForEach(item =>
+                        {
+                            if (!AppServicePlan.Tags.ContainsKey(item.Key))
+                            {
+                                AppServicePlan.Tags.Add(item);
+                            }
+                            else
+                            {
+                                AppServicePlan.Tags[item.Key] = item.Value;
+                            }
+                        });
+                    else if (Tag != null)
                         AppServicePlan.Tags = (IDictionary<string, string>)CmdletHelpers.ConvertToStringDictionary(Tag);
                     break;
             }