This module allows root autoLogin, so we would break that for users, but
they shouldn't be using it anyways. This gives the impression like auto
is some special display manager, when it's just lightdm and special pam
rules to allow root autoLogin. It was created for NixOS's testing
so I believe this is where it belongs.
The switch from slim to lightdm in #30890 broke some nixos tests
because lightdm by default doesn't permit auto-login for root.
Override /etc/pam.d/lightdm-autologin to allow it.
Switch from slim to lightdm as the display-manager.
If plasma5 is used as desktop-manager use sdddm.
If gnome3 is used as desktop-manager use gdm.
Based on #12516
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
