LPS-50946 translate folder id
LPS-50946 LPS-51548 pass in correct repository ID
LPS-50946 represent root folder with null

When a method expects a Folder instance but we need to work with the
root folder, pass null.

Note that a story has been created (LPS-51803) to treat the root folder
as any other regular folder. Once that is implemented, this fix will be
cleaned up.
LPS-50946 SF