Add override MapContent to Mapped Identity Service

Description

Fixed an issue where the wrong asset was chosen when picking an asset from Optimizely Content Marketing Platform (CMP). If contents were imported with CMP Digital Asset Manager (DAM) package, you should run the following script. 

UPDATE [dbo].[tblMappedIdentity]
   SET [ExistingContentId] = NULL
 WHERE [ExistingContentId] IS NOT NULL AND [Provider] = 'dam'