public FailoverInvoiceCollection Get()
        {
            ExternalInvoice[] Invoices = new ExternalInvoice[] {
                new ExternalInvoice()
                {
                    TotalAmount = 5000, Year = DateTime.Now.Year
                },
                new ExternalInvoice()
                {
                    TotalAmount = 7000, Year = DateTime.Now.AddYears(-1).Year
                },
                new ExternalInvoice()
                {
                    TotalAmount = 8000, Year = DateTime.Now.AddYears(-2).Year
                },
                new ExternalInvoice()
                {
                    TotalAmount = 9000, Year = DateTime.Now.AddYears(-3).Year
                }
            };
            FailoverInvoiceCollection collection = new FailoverInvoiceCollection()
            {
                Timestamp = DateTime.Now,
                Invoices  = Invoices
            };

            return(collection);
        }
        public FailoverInvoiceCollection GetInvoices(int supplierId)
        {
            FailoverInvoiceCollection collection = _storageRepository.Get();

            if (DateTime.Now.Year - collection.Timestamp.Year == 0 && DateTime.Now.Month - collection.Timestamp.Month <= 1)
            {
                return(collection);
            }
            else
            {
                return(new FailoverInvoiceCollection());
            }
        }