checked in a Debian trixie container with the PAM realm plugin: without
/etc/pam.d/proxmox-ve-auth, a user with an empty password could log in
with any password, as in the bug. with a copy of /etc/pam.d/other, with
common-auth inlined without 'nullok', this login failed, while the one
of a user with a password still worked.

rendered the chapter with asciidoc, without new warnings.