public int RegisterNewClient(ClientRegistrationInfo args)
        {
            var entityToAdd = (new ClientEntity()
            {
                RegistationDateTime = DateTime.Now,
                Name = args.Name,
                Phone = args.Phone,
                Balance = 0M
            });

            if (clientTableRepository.Contains(entityToAdd))
            {
                throw new ArgumentException("This client has been already registered");
            }
            clientTableRepository.Add(entityToAdd);
            clientTableRepository.SaveChanges();
            return(entityToAdd.Id);
        }