Dunning information on Invoice: API should return same data as ERP UI

[jnemo]

https://community.visma.com/t5/Forum-in-Developers-Visma-net/Obtaining-DunningLevelInformation/m-p/4...

tldr linked post:

The ERP UI displays different information for seemingly the same fields on an CustomerInvoice. Via API we're currently unable to differentiate between Invoices with dunning letter drafts and released ones.

Vismanet swagger doc even says:

The Financial details tab > The dunning info section > Dunning level > The dunning level of the document

We have no strong preference on the specific solution. Possibly an easy one is that API should filter the dunning information like ERP does.