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

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

            var tasks = await _toDoListTaskService.GetUnfinishedTasksAsync(currentUser);

            var model = new ToDoListViewModel()
            {
                Tasks = tasks
            };

            return(View(model));
        }