Updated the output types to support the v2 transfer-only

I needed the v2 API Transfer-Only output type so I added that in here. Switched up the attributes being used because it seemed nicer to go with OOTB attributes then modifying the custom serializer you had, but makes no difference to me as long as "transfer-only" works (since that's not a valid enum name I had to go with the specific names on the enums).