Add gdm gnome sddm kde

modules/programs/gdm.nix

@@ -0,0 +1,34 @@
+{
+  lib,
+  options,
+  config,
+  ...
+}:
+{
+  options.mods.gdm = {
+    enable = lib.mkOption {
+      default = false;
+      example = true;
+      type = lib.types.bool;
+      description = "Enables the gdm displayManager";
+    };
+    extraOptions = lib.mkOption {
+      default = { };
+      example = { };
+      type = with lib.types; attrsOf anything;
+      description = "Extra options to be applied to the gnome config";
+    };
+  };
+
+  config = lib.mkIf config.mods.gdm.enable (
+    lib.optionalAttrs (options ? services.xserver.displayManager.gdm) (
+      {
+        services.xserver.enable = true;
+        services.xserver.displayManager.gdm.enable = true;
+      }
+      // {
+        services.xserver.displayManager.gdm = config.mods.gdm.extraOptions;
+      }
+    )
+  );
+}