[ceph-users] Documentation for meaning of "tag cephfs" in OSD caps

Hello In https://docs.ceph.com/en/latest/cephfs/client-auth/ we can find that ceph fs authorize cephfs_a client.foo / r /bar rw Results in client.foo   key: *key*   caps:  [mds]  allow  r,  allow  rw  path=/bar   caps:  [mon]  allow  r   caps:  [osd]  allow  rw  tag  cephfs  data=cephfs_a What is this "tag cephfs" thing? It seems like some undocumented black magic to me, since I can't find anything that documents it. Can someone explain how it works under the hood? What does it expand to? What does it limit and how?