some modularizing and refactoring

modules/nixos/system/xdg/default.nix

@@ -0,0 +1,37 @@
+{
+  lib,
+  config,
+  pkgs,
+  ...
+}: let
+  inherit (lib) mkIf mkOption mkEnableOption types;
+  cfg = config.nixos.system.xdg;
+in {
+  options = {
+    nixos.system.xdg = {
+      enable = mkEnableOption "Enable XDG portal.";
+      xdgOpenUsePortal = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Use xdg-open via the portal.";
+      };
+      extraPortals = mkOption {
+        type = types.listOf types.package;
+        default = [pkgs.xdg-desktop-portal-gtk];
+        description = "List of extra portals to include.";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    xdg.portal = {
+      enable = true;
+      xdgOpenUsePortal = cfg.xdgOpenUsePortal;
+      config = {
+        common.default = ["gtk"];
+        hyprland.default = ["gtk" "hyprland"];
+      };
+      extraPortals = cfg.extraPortals;
+    };
+  };
+}