public ActionResult <IEnumerable <CustomerReadDto> > CreateCustomers(IEnumerable <CustomerCreateDto> customerCreateDtos)
        {
            // TODO: add validations as - at least 1 entity arrived, sex is either 'M' or 'F', etc..

            var customers = _mapper.Map <IEnumerable <Customer> >(customerCreateDtos);

            _customerRepo.CreateCustomers(customers);
            _customerRepo.SaveChanges();

            var customersIds = customers.Select(x => x.Id).ToArray();

            var customersFromRepo = _customerRepo.GetCustomersByIds(customersIds);

            if (customersFromRepo.All(x => x != null))
            {
                return(Ok(_mapper.Map <IEnumerable <CustomerReadDto> >(customersFromRepo)));
            }
            return(NotFound());
        }