public async Task<IHttpActionResult> Create(TodoItemEditModel model)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest();
            }

            var todo = new TodoItem
            {
                Title = model.Title,
                IsDone = model.IsDone,
                IsPublic = model.IsPublic,
                AttendeeEmail = model.AttendeeEmail
            };

            db.ToDoItems.Add(todo);
            await db.SaveChangesAsync();
            return Ok(todo.Id);
        }
        public async Task<IHttpActionResult> Edit(Guid id, TodoItemEditModel model)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest();
            }

            var todo = await db.ToDoItems.SingleOrDefaultAsync(x => x.Id == id);
            if (todo == null)
            {
                return NotFound();
            }

            todo.Title = model.Title;
            todo.IsDone = model.IsDone;
            todo.IsPublic = model.IsPublic;
            todo.AttendeeEmail = model.AttendeeEmail;

            await db.SaveChangesAsync();
            return Ok();
        }