manual setting of invoice date doesn't lead to a change of next payment date [account_payment_discount_extension]

[Thorsten Vocks (OpenBig.org)]

Use case:

1. New Supplier Invoice
2. Manual setting of invoice date (for instance 4 days in the past)

If i do this opening of the invoice leads to follwing result in the field
"Next Payment date" which is essential to calculate "just in time" payments checking best
day to pay controled via estimated next payment day (Click on Select Invoices to pay entering in
field due date the day when you expect to create next payment proposal).

I would expect for my use case following calculation: Invoice date + current cash disocunt days (for example 10 days)

In fact the system seems to calculate this way: Creation Date of invoice + current cash discount days (for example 10 days).

[Thomas Dreiling (thomas-dreiling)]

fix provided in https://bugs.launchpad.net/bigconsulting/+bug/639645