polkit: properly enable it and enable gnome-keyring

nixos.nix

@@ -22,6 +22,7 @@ in
     ./hardware-configuration.nix
     # Include service configuration
     ./services/archi.nix
+    ./services/authentication.nix
     ./services/caddy.nix
     ./services/forgejo.nix
     ./services/jellyfin.nix

services/authentication.nix

@@ -0,0 +1,12 @@
+{ pkgs, ... }:
+
+{
+  # Enable polkit,
+  security.polkit.enable = true;
+
+  # Install an agent to interface with it.
+  environment.systemPackages = with pkgs; [ polkit_gnome ];
+
+  # And enable GNOME keyring for registering keys.
+  services.gnome.gnome-keyring.enable = true;
+}