refactor: make modules independant and exposed in the flake for outside use

nixosModules/adb/default.nix

@@ -0,0 +1,27 @@
+{
+  config,
+  lib,
+  ...
+}: let
+  inherit (lib) mkIf mkOption types;
+
+  cfg = config.programs.adb;
+in {
+  options.programs.adb = {
+    user = mkOption {
+      type = types.str;
+      default = "root";
+      description = ''
+        The name of the user who is going to interact with
+        the android devices.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    users.users.${cfg.user}.extraGroups = ["adbusers"];
+  };
+
+  # For accurate stack trace
+  _file = ./default.nix;
+}