[FUSE] rmdir on CollectionDirectory sets expires_at
As of this writing, if you rmdir a CollectionDirectory in FUSE, it uses the collections/delete API. Instead, it should calculate a timestamp that is
defaultTrashLifetime (or, if that's not set in the discovery document,
blobSignatureTtl) seconds in the future, and update the collection's
expires_at attribute to that value. The CollectionDirectory should still be removed from its parent, as now, because expiring collections do not appear in most directory listings (see #9584).