Add a bluetooth role.

nix/configuration/roles/bluetooth/default.nix

@@ -0,0 +1,46 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+{
+  imports = [ ];
+
+  options.me = {
+    bluetooth.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to install bluetooth.";
+    };
+  };
+
+  config = lib.mkIf config.me.bluetooth.enable (
+    lib.mkMerge [
+      {
+        environment.systemPackages = with pkgs; [
+        ];
+
+        hardware.bluetooth = {
+          enable = true;
+          powerOnBoot = true;
+          settings = {
+            General = {
+              # Enable support for showing battery charge level.
+              Experimental = true;
+            };
+          };
+        };
+
+        environment.persistence."/persist" = lib.mkIf (!config.me.buildingIso) {
+          hideMounts = true;
+          directories = [
+            "/var/lib/bluetooth" # Bluetooth pairing information.
+          ];
+        };
+      }
+    ]
+  );
+}