Some doc http://docs.nethserver.org/projects/nethserver-devel/en/latest/directory.html
And a concret example https://github.com/stephdl/nethserver-BackupPC/blob/ns6/root/etc/e-smith/templates/etc/httpd/conf.d/BackupPC.conf/10base
In fact you use the user ‘libuser’ and the password is in /var/lib/nethserver/secret