private void GenerateInvoice(Activity activity)
        {
            if (activity is null)
            {
                return;
            }

            List <Service> services = activity.ActivitiesServices.Select(s => s.Service).ToList();

            ServiceInvoice serviceInvoice = new ServiceInvoice
            {
                Client         = activity.Client,
                ClientId       = activity.ClientId,
                PaymentMethod  = PaymentMethod.None,
                State          = InvoiceState.Generated,
                IVA            = 0.19M,
                GenerationDate = DateTime.Now
            };

            services.ForEach(service => { serviceInvoice.AddDetail(service); });

            serviceInvoice.CalculateTotal();

            _serviceInvoicesRepository.Insert(serviceInvoice);
        }