Add relation sales invoice - dunning document

[metas-dh]

Is this a bug or feature request?

FR

What is the current behavior?

Atm there is no relation between the dunning document and the resp. sales invoice(s) that get dunned. Relation dunning document - dunning candidate is not working.

Which are the steps to reproduce?

Create a dunning document for 1 or more sales invoices, from dunning candidates, and check the dunning document: no relation or any info for which invoice(s) the dunning doc was created. No relation in sales invoice to dunning doc either.

What is the expected or desired behavior?

Relation between sales invoice - dunning document, back and forth (=> reference!).

[metas-dh]

IT successful.