Missing documentation for payment reference attribute #160
Description
Apparently the reference attribute for payments created via the /payments endpoint must be a valid Finnish bank reference (pankkiviite) if per-transaction settlement (individual settlement) is used. This is not mentioned in the docs where it just says that reference should be a string of max 200 characters.
If per-transaction settlement is active and the submitted reference is not a valid bank reference, the Paytrail API will respond with "Given reference did not pass Finnish reference number validation".
This constraint for the reference attribute should be mentioned in the docs.