onUpdateMediaNotificationMetadata    
  open suspend fun onUpdateMediaNotificationMetadata(builder: MediaMetadataCompat.Builder, call: Call, callDisplayName: String? = null): MediaMetadataCompat.Builder
Intercept the media notification metadata builder and modify it before it is posted for updating.
Parameters
builder
The media metadata builder.
call
The Stream call object.
callDisplayName  
The name of the caller to display in the notification.