Large change on folder structure AND used of import-tree.

modules/system/options/nixos/dns.nix

@@ -0,0 +1,20 @@
+{ lib, config, ... }:
+with lib;
+let
+  cfg = config.os.networks.dns;
+in
+{
+  options.os.networks.dns = {
+    enable = mkEnableOption "System dns service";
+  };
+  config = mkIf cfg.enable {
+
+    services.resolved.enable = true;
+
+    services.avahi = {
+      enable = true;
+      nssmdns4 = true;
+    };
+
+  };
+}