PendingReleaseNotes: add note on the client incompatibility health warning and feature bit

Signed-off-by: Patrick Donnelly <[email protected]>

Author: batrick

PendingReleaseNotes

@@ -186,6 +186,13 @@ CephFS: Disallow delegating preallocated inode ranges to clients. Config
   confirmation flag when some MDSs exhibit health warning MDS_TRIM or
   MDS_CACHE_OVERSIZED. This is to prevent accidental MDS failover causing
   further delays in recovery.
+* CephFS: fixes to the implementation of the ``root_squash`` mechanism enabled
+  via cephx ``mds`` caps on a client credential require a new client feature
+  bit, ``client_mds_auth_caps``. Clients using credentials with ``root_squash``
+  without this feature will trigger the MDS to raise a HEALTH_ERR on the
+  cluster, MDS_CLIENTS_BROKEN_ROOTSQUASH. See the documentation on this warning
+  and the new feature bit for more information.
+
 
 >=18.0.0