Update a lot of options, simplify variables, replace options with tags

modules/system/users/default.nix

@@ -1,6 +1,8 @@
-{ lib, ... }:
+{ ... }:
 {
-  imports = [ ./main ];
-
-  options.system.extraUsers.enable = lib.mkEnableOption "Enable a shared system";
+  imports = [
+    ./freecorn
+    ./luna
+    ./main
+  ];
 }