Switch to amount due for Xero invoices

src/Xero.hs

@@ -192,7 +192,7 @@ instance FromJSON XeroInvoice where
       cN <- c .: "Name"
       cu <- obj .: "CurrencyCode"
       cR <- obj .: "CurrencyRate"
-      total <- obj .: "Total"
+      total <- obj .: "AmountDue"
       status <- obj .: "Status"
       d <- obj .: "Date"
       pure $