nixos/clickshare: init module

The clickshare-csc1 package brings a udev rule file
to grant access to the ClickShare dongle if connected.
This module provides an option to install that rule file.
Only users in the "clickshare" users group have access.

nixos/modules/module-list.nix

···
   ./programs/ccache.nix
   ./programs/cdemu.nix
   ./programs/chromium.nix
+  ./programs/clickshare.nix
   ./programs/command-not-found/command-not-found.nix
   ./programs/criu.nix
   ./programs/dconf.nix

nixos/modules/programs/clickshare.nix

···
+{ config, lib, pkgs, ... }:
+
+{
+
+  options.programs.clickshare-csc1.enable =
+    lib.options.mkEnableOption ''
+      Barco ClickShare CSC-1 driver/client.
+      This allows users in the <literal>clickshare</literal>
+      group to access and use a ClickShare USB dongle
+      that is connected to the machine
+    '';
+
+  config = lib.modules.mkIf config.programs.clickshare-csc1.enable {
+    environment.systemPackages = [ pkgs.clickshare-csc1 ];
+    services.udev.packages = [ pkgs.clickshare-csc1 ];
+    users.groups.clickshare = {};
+  };
+
+  meta.maintainers = [ lib.maintainers.yarny ];
+
+}