Extract IPTSd management into new option-enabled module

microsoft/surface/common/ipts/default.nix

@@ -0,0 +1,27 @@
+{ config, lib, pkgs, ... }:
+
+let
+  inherit (lib) mkDefault mkEnableOption mkIf mkMerge;
+
+  cfg = config.microsoft-surface.ipts;
+
+in {
+  options.microsoft-surface.ipts = {
+    enable = mkEnableOption "Enable IPTSd for Microsoft Surface";
+  };
+
+  config = mkMerge [
+    {
+      microsoft-surface.ipts.enable = mkDefault false;
+    }
+
+    (mkIf cfg.enable {
+      systemd.services.iptsd = {
+        description = "IPTSD";
+        path = with pkgs; [ iptsd ];
+        script = "iptsd";
+        wantedBy = [ "multi-user.target" ];
+      };
+    })
+  ];
+}