Description of problem:

The current Ceph Object Gateway LDAP authentication documentation does not explain the new custom ldap search filter parameter

Version-Release number of selected component (if applicable):

>= 2.2

How reproducible:

n/a

Expected results:

The following upstream doc contains the missing parameter explanation in the section "Using a custom search filter to limit user access": https://github.com/ceph/ceph/blob/master/doc/radosgw/ldap-auth.rst

Additional info:

Please contact me if further information or explanation is needed