Trivial Description
The UserImporter logs a misleading warning when unable to handle a property unrelated to user/group import. Since the ProtectedItemImporter implementation are just asked to handle a given protected item, it's confusing to mark this a WARNing, it should just be for information purpose on DEBUG level.
While reviewing this I also got the impression that the importer is too verbose wrt besteffort handling of group membership. Would suggest to set this from INFO to DEBUG too.