public Book(Guid id, Guid customerId, Guid productId, int reserveDaysCount)
{
CustomValidator.ValidateNumber(reserveDaysCount, 1, 7);
CustomValidator.ValidateId(id);
CustomValidator.ValidateId(customerId);
CustomValidator.ValidateId(productId);
Id = id;
CustomerId = customerId;
ProductId = productId;
CreationTime = DateTimeOffset.UtcNow;
ExpirationTime = CreationTime.AddDays(reserveDaysCount);
ReserveDaysCount = reserveDaysCount;
}
public bool IsValid() => CreationTime.AddDays(1d).CompareTo(DateTime.Now) > 0;