MAN: Document the re_expression needed to suport @-signs in the groupnames
In the 2.0 release we will be able to change the default regular
expression that will allow to consume @-signs in the name, but
since the 1.x branches need to stay backwards compatible, let's
only document the regex for now.
Related:
https://pagure.io/SSSD/sssd/issue/3219
Reviewed-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Sumit Bose <sbose@redhat.com>