[16.0] grouping doesn't take into account the mandate nor sequence type

[alexis-via]

I found this bug while reading the code of OCA/bank-payment... then I tested the corresponding scenario and it confirmed the bug.

Here is the scenario:

• create a new customer with 1 bank account. Set customer payment mode to SEPA direct debit. Create 2 mandates linked to that bank account.
• create a customer invoice for that new customer with mandate 1.
• create a customer invoice for that new customer with mandate 2.
• add the 2 customer invoices to a new direct debit order. Confirm that debit order: you will see a single account.payment, instead of 2. When you generate the XML file, you will have only 1 transaction linked to only 1 of the 2 mandates.

[github-actions]

There hasn't been any activity on this issue in the past 6 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
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[alexis-via]

I just found another related issue while working on OCA/bank-payment-alternative: the grouping of account.payment.line in account.payment doesn't take into account the sequence type !