Add backup-helper to test host

hosts/nixos-test1/configuration.nix

@@ -50,6 +50,18 @@
   # Or disable the firewall altogether.
   networking.firewall.enable = false;
 
+  # Secrets
+  # Backup helper
+  sops.secrets."backup_helper_secret" = { };
+  backup-helper = {
+    enable = true;
+    password-file = "/run/secrets/backup_helper_secret";
+    backup-dirs = [
+      "/etc/machine-id"
+      "/etc/os-release"
+    ];
+  };
+
   system.stateVersion = "23.11"; # Did you read the comment?
 }