flatpak: Move to common instead of being machine-specific

common/default.nix

@@ -5,6 +5,7 @@
     agenix.nixosModules.default
 
     ./backup.nix
+    ./flatpak.nix
     ./http.nix
     ./mail.nix
     ./monitoring.nix

common/flatpak.nix

@@ -0,0 +1,18 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.my.flatpak;
+in {
+  options.my.flatpak.enable = lib.mkEnableOption "Flatpak";
+
+  config = lib.mkIf cfg.enable {
+    # Needed for Flatpak.
+    xdg.portal = {
+      enable = true;
+      extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
+      config.common.default = "gtk";
+    };
+
+    services.flatpak.enable = true;
+  };
+}

machines/altair/default.nix

@@ -7,7 +7,6 @@ in {
     my.modules
 
     ./emulation.nix
-    ./flatpak.nix
     ./hypervisor.nix
     ./hardware.nix
     ./postgres.nix
@@ -34,6 +33,8 @@ in {
   networking.domain = "dolphin-emu.org";
   networking.search = [ "dolphin-emu.org" ];
 
+  my.flatpak.enable = true;
+
   my.roles = {
     analytics.enable = true;
     android-updater.enable = true;

machines/altair/flatpak.nix

@@ -1,12 +0,0 @@
-{ pkgs, ... }:
-
-{
-  # Needed for Flatpak.
-  xdg.portal = {
-    enable = true;
-    extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
-    config.common.default = "gtk";
-  };
-
-  services.flatpak.enable = true;
-}