public async Task <IActionResult> DeleteValue(DeleteValueModel model)
        {
            var currentUser = await _userManager.GetUserAsync(User);

            if (currentUser == null)
            {
                return(Challenge());
            }

            Guid[] deletedValues = null;

            var succeeded = await _appService.DeleteVariableAsync(currentUser, model, (x) => deletedValues = x);

            return(Json(new { success = succeeded, values = deletedValues }));
        }