public async Task <InvoiceWithClient> GenerateInvoiceForNewClientAsync(Invoice invoice, Client client)
        {
            var clientWithId = await clients.CreateAsync(client);

            invoice.Client_uid = clientWithId.Id;
            var invoiceWithId = await invoices.CreateAsync(invoice);

            return(new InvoiceWithClient
            {
                Client = clientWithId,
                Invoice = invoiceWithId,
            });
        }