public ToDoList CreateToDoList(ToDoListDTO list, string owner)
        {
            ToDoList result = list.ToEntity();

            result.Position = _context.ToDoLists.Where(l => l.Owner == owner).Count();
            result.Reminded = true;
            result.Owner    = owner;
            _context.ToDoLists.Add(result);
            _context.SaveChanges();

            return(result);
        }
        public void UpdateToDoList(ToDoListDTO list, string owner)
        {
            ToDoList oldList = GetToDoList(list.Id, owner);

            if (oldList == null)
            {
                throw new EntityNotFoundException();
            }
            else if (oldList.Owner != owner)
            {
                throw new UnauthorizedException();
            }

            oldList.Update(list.ToEntity());
            _context.SaveChanges();
        }