sale_partner_incoterm: Default incoterm does not propagate to contacts at company

[Crazor]

Module

sale_partner_incoterm

Describe the bug

When I set a default incoterm on a company, I expect that any new quotations created inherit that incoterm, no matter which person at that company I address that quotation to.

To Reproduce

Affected versions: tested on 17

Steps to reproduce the behavior:

1. Set default incoterm on a company
2. Observe that none of that company's contacts has a default incoterm set (this is ok)
3. Create a new sales quotation, choose the company itself, observe that the default incoterm has automatically been set on the quotation
4. Create another new sales quotation, choose any of the company's contacts, observe that the default incoterm was not set

Expected behavior
I would expect that the company's default sales incoterm be applied regardless of which contact I address the sales quotation too. The only exception would be if a contact at a company already has a default incoterm set.

Additional context
This behaviour possibly also affects purchase_partner_incoterm, although I haven't tested that yet.

Note that I am using the recently approved version from #2968, even though it hasn't been merged yet.