Add opinioated defaults setting

modules/default.nix

@@ -0,0 +1,5 @@
+{ lib, ... }:
+
+{
+  options.opinionatedDefaults = lib.mkEnableOption "opinionated defaults";
+}

modules/nginx.nix

@@ -3,7 +3,7 @@
 {
   options.services.nginx.openFirewall = lib.mkOption {
     type = lib.types.bool;
-    default = false;
+    default = config.opinionatedDefaults;
     description = lib.mdDoc "Wether to open the firewall port for the http (80) and https (443) default ports.";
   };