modules/nixos/system: add headless and minimal modules

modules/nixos/system/headless.nix

@@ -0,0 +1,21 @@
+{ config, ... }:
+
+{
+  # https://github.com/NixOS/nixpkgs/blob/nixos-unstable/nixos/modules/profiles/headless.nix
+
+  systemd.services = {
+    "serial-getty@ttyS0".enable = false;
+    "serial-getty@hvc0".enable = false;
+    "getty@tty1".enable = false;
+    "autovt@".enable = false;
+  };
+
+  boot.kernelParams = [
+    "panic=1"
+    "boot.panic_on_fail"
+    "vga=0x317"
+    "nomodeset"
+  ];
+  
+  systemd.enableEmergencyMode = false;
+}

modules/nixos/system/minimal.nix

@@ -0,0 +1,18 @@
+{ config, ... }:
+
+{
+  # see modules/common/debloat.nix
+
+  documentation = {
+    enable = false;
+    man.enable = false;
+    nixos.enable = false;
+  };
+
+  xdg = {
+    autostart.enable = false;
+    icons.enable = false;
+    mime.enable = false;
+    sounds.enable = false;
+  };
+}