[18.0] SEPA Credit Transfer using Bill reference as communication

[jusle]

Module

account_banking_sepa_credit_transfer

Describe the bug

When creating a payment order, if the vendor bill has both bill reference and payment reference defined, the transaction is picking the vendor bill reference to the communication field, instead of the payment reference.

To Reproduce

Affected versions: 18.0

Steps to reproduce the behavior:

1. Set Payment Mode on vendor bill.
2. Go to: Accounting -> Vendors -> Payment Orders -> New.
3. Select the Payment Mode -> Create Payment Lines from Journal Items.
4. Select Add All Move Lines -> Create Transactions.
   or, click "Add to Payment Order" on a vendor bill.

Expected behavior
If there is a payment reference in the vendor bill, the payee is expecting to receive the payment with the payment reference, although their bill has a reference. Thus, the logic should be other way around: By default, pick the payment reference, and if there is no payment reference, pick the bill reference.