Backfill the Az.8.0.0 migration guide for Az.Cdn (#22779)

* Backfill the Az.8.0.0 migration guide for Az.Cdn

* Update ChangeLog of Az.Cdn

* Update main ChangeLog file

Author: TracyYaoYao

ChangeLog.md

@@ -2114,6 +2114,7 @@ for a better powershell experience and as a result would witness breaking change
   - Update-AzFrontDoorCdnCustomDomainValidationToken
   - Update-AzFrontDoorCdnRule
 * Renamed Set cmdlets to Update cmdlets
+* Renamed 'Unpublish-AzCdnEndpointContent' cmdlets to 'Clear-AzCdnEndpointContent'
 * Added 'Object' suffix to memory object creation cmdlets
 
 #### Az.Compute

documentation/migration-guides/Az.8.0.0-migration-guide.md

@@ -206,6 +206,34 @@ Update-AzCdnOrigin -ResourceGroupName $resourceGroupName -ProfileName $cdnProfil
     -Name $originName  -HostName "mystorage2.blob.core.windows.net" -HttpPort 456 -HttpsPort 789           
 ```
 
+### `Unpublish-AzCdnEndpointContent`
+Replaced by command `Clear-AzCdnEndpointContent`
+
+#### Before
+```powershell
+Unpublish-AzCdnEndpointContent -ResourceGroupName $resourceGroupName -ProfileName $cdnProfileName -EndpointName $endpointName `
+   -PurgeContent $PurgeContent   
+```
+#### After
+```powershell
+Clear-AzCdnEndpointContent -ResourceGroupName $resourceGroupName -ProfileName $cdnProfileName -EndpointName $endpointName `
+   -ContentPath $PurgeContent   
+```
+
+### `Publish-AzCdnEndpointContent`
+Replaced by command `Import-AzCdnEndpointContent`
+
+#### Before
+```powershell
+Publish-AzCdnEndpointContent -ResourceGroupName $resourceGroupName -ProfileName $cdnProfileName -EndpointName $endpointName `
+   -LoadContent $LoadContent
+```
+#### After
+```powershell
+Import-AzCdnEndpointContent -ResourceGroupName $resourceGroupName -ProfileName $cdnProfileName -EndpointName $endpointName `
+   -ContentPath $LoadContent
+```
+
 ## Az.EventHub
 
 ### `New-AzEventHubNamespace`

src/Cdn/ChangeLog.md

@@ -51,6 +51,7 @@
   - Update-AzFrontDoorCdnCustomDomainValidationToken
   - Update-AzFrontDoorCdnRule
 * Renamed Set cmdlets to Update cmdlets
+* Renamed `Unpublish-AzCdnEndpointContent` cmdlets to `Clear-AzCdnEndpointContent`
 * Added `Object` suffix to memory object creation cmdlets
 
 ## Version 1.8.3