Changed option namespace for better compatibility

modules/systems/ssh.nix

@@ -0,0 +1,21 @@
+{ config, lib, ... }:
+let
+  cfg = config.my.systems.ssh;
+in
+{
+  options.my.systems.ssh = {
+    enable = lib.mkEnableOption "Enable SSH Server";
+  };
+
+  config = lib.mkIf cfg.enable {
+
+    services.openssh = {
+      enable = true;
+
+      # require public key authentication for better security
+      settings.PasswordAuthentication = false;
+      settings.KbdInteractiveAuthentication = false;
+      settings.PermitRootLogin = false;
+    };
+  };
+}