ADD automatic gc

configuration.nix

···
     randomizedDelaySec = "45min";
   };
 
+  # Automatic Garbage Collection
+  nix.gc.automatic = true;
+  nix.gc.options = "--delete-older-than 8d";
+
   # This option defines the first version of NixOS you have installed on this particular machine,
   # and is used to maintain compatibility with application data (e.g. databases) created on older NixOS versions.
   #