Enable automatic upgrade

birne/configuration.nix

@@ -12,6 +12,7 @@
       <modules/base.nix>
       <modules/desktop.nix>
       <modules/printing.nix>
+      <modules/autoupdate.nix>
     ];
 
   # setup the NIX_PATH so modules from the repo found

modules/autoupdate.nix

@@ -0,0 +1,10 @@
+{ pkgs, config, ... }:
+
+{
+  system.autoUpgrade = {
+    enable = true;
+    dates = "12:00";
+    # might need to move this into the configuration of `birne`?
+    allowReboot = true;
+  };
+}