scanner support: create scanner group. Users need to be in this group to access scanners.

modules/misc/ids.nix

@@ -131,6 +131,7 @@ in
     spamd = 56;
     networkmanager = 57;
     nslcd = 58;
+    scanner = 59;
 
     # When adding a gid, make sure it doesn't match an existing uid.
 

modules/services/hardware/sane.nix

@@ -29,6 +29,12 @@ with pkgs.lib;
       in mkIf config.hardware.sane.enable {
            environment.systemPackages = [ pkg ];
            services.udev.packages = [ pkg ];
+           
+           users.extraGroups = singleton {
+             name = "scanner";
+             gid = config.ids.gids.scanner;
+           };
+
       };
 
 }