Dutch postcode validation for Partners

When you type or change the postcode (or the country) on a contact/partner form, this module automatically checks the value.

• It only acts when the partner's country is the Netherlands; for any other country nothing happens.
• If the postcode is valid, Odoo rewrites it in the official Dutch format, for example "1234ab" becomes "1234 AB".
• If the postcode is not valid, a warning pop-up appears saying that the postcode you entered is not valid. The warning does not stop you from saving the record.

The check runs as an on-change behaviour on the res.partner model, so it is triggered while filling in the form, not as a hard database constraint. The validation itself relies on the external stdnum library; if that library is not installed, the check is simply skipped.

There are no new menus, buttons, reports or scheduled actions. The module only extends the existing partner form and touches the res.partner model. A technical flag (skip_postcode_check in the context) can be used by other code to bypass the check, but this is not something a normal user sees.