Autologin by startxfce4 with no display manager

I’m a new NixOS user and I’m studying the documentation about how config file works. Currently I’m trying to create an ISO file and my purpose is to run an XFCE environment that autologin by a specific user directly to the Live Environment by using startxfce4 instead of startx and with no display manager. By reading Nix docs I cannot find currently a useful attribute to obtain this autologin by startxfce4.

The iso.nix config file piece of code is:

    xserver = {
      enable = true;
      autorun = false;
      layout = "us";
      xkbVariant = "";
      libinput.enable = true;
      desktopManager = {
        xfce.enable = true;
        xfce.enableXfwm = true;
      displayManager.defaultSession = "xfce";