[feat] Support multiple validation errors

[cnblogs-dudu]

Code is worth a thousand words.

public record CreateOrderCommand(CreateOrderDto Dto, bool ValidateOnly)
    : ICommand<long, OrderError>, IValidatable
{
    public IEnumerable<ValidationError>? Validate()
    {
        ICollection<ValidationResult>? results = null;
        if (!Validator.TryValidateObject(Dto, new ValidationContext(Dto), results, true))
        {
            return results?.Select(r => new ValidationError(r.ErrorMessage, r.MemberNames.First()));
        }

        return null;
    }
}