Can update virtual directory

lib/helpers/settings_helper.dart

@@ -64,6 +64,16 @@ class SettingsHelper {
         .assertOk();
   }
 
+  /// Check out whether a virtual directory is available for a user or not
+  ///
+  /// Throws in case of failure
+  static Future<void> checkUserDirectoryAvailability(String dir) async =>
+      (await APIRequest(
+              uri: "settings/check_user_directory_availability",
+              needLogin: true,
+              args: {"directory": dir}).exec())
+          .assertOk();
+
   /// Get & return account image settings
   static Future<AccountImageSettings> getAccountImageSettings() async {
     final response =