public void AddBuyer(Buyer buyer)
        {
            if (buyer == null)
            {
                throw new ArgumentNullException(nameof(buyer));
            }

            var currentBuyer = _buyerRepository.GetById(buyer.Id);

            if (currentBuyer != null)
            {
                throw  new Exception("Buyer already exist.");
            }

            currentBuyer.Name = "joao";

            buyer.AddContact(new Contact()
            {
                Description = "michel"
            });

            _buyerRepository.Add(buyer);

            _unityOfWork.Commit();
        }