nixos/gnome: Install GNOME Software using module

gnome-software now uses systemd instead of autostart so we need to add it to `systemd.packages`:
0880577507

nixos/modules/module-list.nix

@@ -569,6 +569,7 @@
   ./services/desktops/gnome/gnome-online-miners.nix
   ./services/desktops/gnome/gnome-remote-desktop.nix
   ./services/desktops/gnome/gnome-settings-daemon.nix
+  ./services/desktops/gnome/gnome-software.nix
   ./services/desktops/gnome/gnome-user-share.nix
   ./services/desktops/gnome/localsearch.nix
   ./services/desktops/gnome/rygel.nix

nixos/modules/services/desktop-managers/gnome.nix

@@ -444,8 +444,7 @@ in
 
     # Adapt from https://gitlab.gnome.org/GNOME/gnome-build-meta/-/blob/gnome-48/elements/core/meta-gnome-core-apps.bst
     (lib.mkIf serviceCfg.core-apps.enable {
-      environment.systemPackages = utils.removePackagesByName (
-        [
+      environment.systemPackages = utils.removePackagesByName [
         pkgs.baobab
         pkgs.decibels
         pkgs.epiphany
@@ -469,13 +468,7 @@ in
         pkgs.snapshot
         pkgs.totem
         pkgs.yelp
-        ]
-        ++ lib.optionals config.services.flatpak.enable [
-          # Since PackageKit Nix support is not there yet,
-          # only install gnome-software if flatpak is enabled.
-          pkgs.gnome-software
-        ]
-      ) config.environment.gnome.excludePackages;
+      ] config.environment.gnome.excludePackages;
 
       # Enable default program modules
       # Since some of these have a corresponding package, we only
@@ -488,6 +481,12 @@ in
       programs.seahorse.enable = notExcluded pkgs.seahorse;
       services.gnome.sushi.enable = notExcluded pkgs.sushi;
 
+      # Since PackageKit Nix support is not there yet,
+      # only install gnome-software if flatpak is enabled.
+      services.gnome.gnome-software.enable = lib.mkIf config.services.flatpak.enable (
+        notExcluded pkgs.gnome-software
+      );
+
       # VTE shell integration for gnome-console
       programs.bash.vteIntegration = mkDefault true;
       programs.zsh.vteIntegration = mkDefault true;

nixos/modules/services/desktops/gnome/gnome-software.nix

@@ -0,0 +1,28 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
+
+{
+  meta = {
+    maintainers = lib.teams.gnome.members;
+  };
+
+  options = {
+    services.gnome.gnome-software = {
+      enable = lib.mkEnableOption "GNOME Software, package manager for GNOME";
+    };
+  };
+
+  config = lib.mkIf config.services.gnome.gnome-software.enable {
+    environment.systemPackages = [
+      pkgs.gnome-software
+    ];
+
+    systemd.packages = [
+      pkgs.gnome-software
+    ];
+  };
+}