delivery_zone_id is not automatically set when creating an so

[chielos24]

Module

partner_delivery_zone

Describe the bug

delivery_zone_id is not automatically set when creating an so. Or

To Reproduce

Affected versions:

Steps to reproduce the behavior:

1. Go to Sales > Orders > Customers.
2. Choose a customer.
3. Click on 'Edit' button.
4. Go to Sales & Purchase tab.
5. In 'Delivery Zone' field select an option for this partner.
6. Click on 'Save' button to apply changes.
7. Go to Sales > Orders > Quotations.
8. Create a quotation. 'Delivery zone' field is automatically filled. >> this is not set.

Additional context
Version 18, installed on ubuntui

Possible explaination
I tested again, and the Zone is taken from the delivery address, not from the main partner itself. That explains it! But then we need to update the readme file.