[cwconfig] add the CubicWebConfiguration.ensure_uid_directory() method (related to #11298794)
that recursively enforce uid on files.
from cubicweb.predicates import is_instance
from cubicweb.hooks import notification
class FolderUpdateHook(notification.EntityUpdateHook):
__select__ = (notification.EntityUpdateHook.__select__ &
is_instance('Folder'))
order = 100 # late trigger so that metadata hooks come before.