add flatpaks with nix-flatpak

modules/system/default.nix

@@ -15,6 +15,7 @@
     ./vpn-confinement
     ./syncthing
     ./graphics
+    ./flatpak
   ];
 
   system.ssh.enable = lib.mkDefault true;

modules/system/flatpak/default.nix

@@ -0,0 +1,19 @@
+{
+  pkgs,
+  inputs,
+  config,
+  lib,
+  ...
+}: let
+  cfg = config.system.flatpak;
+in {
+  options.system.flatpak = {
+    enable = lib.mkEnableOption "enables nix-flatpak on nixos side";
+  };
+
+  imports = [inputs.nix-flatpak.nixosModules.nix-flatpak];
+
+  config = lib.mkIf cfg.enable {
+    services.flatpak.enable = true;
+  };
+}