chore: refactor system modules

system/services/endlessh.nix

@@ -0,0 +1,21 @@
+{
+  config,
+  lib,
+  ...
+}:
+with lib; let
+  cfg = config.system.services.endlessh;
+in {
+  options.system.services.endlessh = {
+    enable = mkEnableOption "Enables endlessh.";
+    port = mkOption {
+      type = types.port;
+      default = 2222;
+      example = 22;
+    };
+  };
+  config.services.endlessh-go = mkIf cfg.enable {
+    inherit (cfg) enable port;
+    openFirewall = true;
+  };
+}