Major config overhaul: use custom modules, setup for multi-host config, and less boilerplate

modules/system/security/openvpn/default.nix

@@ -0,0 +1,16 @@
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.systemSettings.security.openvpn;
+in {
+  options = {
+    systemSettings.security.openvpn = {
+      enable = lib.mkEnableOption "Enable openvpn";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    environment.systemPackages = [ pkgs.openvpn ];
+    environment.etc.openvpn.source = "${pkgs.update-resolv-conf}/libexec/openvpn";
+  };
+}