public void AddOne(Purchase item)
    {
        CustomValidator.ValidateObject(item);
        var exists = Exists(item.Id);

        if (!exists)
        {
            var enState = _context.Purchases.Add(_purchaseMapper.DomainToDb(item));
            enState.State = EntityState.Added;
            _context.SaveChanges();
        }
    }
        public async Task AddOne(Purchase item)
        {
            CustomValidator.ValidateObject(item);
            await using var context = new MyDbContext(_options);
            if (!Exists(item.Id))
            {
                var enState = await context.Purchases.AddAsync(_purchaseMapper.DomainToDb(item));

                enState.State = EntityState.Added;
                await context.SaveChangesAsync();
            }
        }