Portal User Login Email Change

This module keeps a portal user's login in sync with their contact email. Normally, a portal user's login is their email address. If the portal user edits the email on their own contact record, the login stored on the linked user account would otherwise stay on the old address, and the user could no longer sign in with the new one.

The module extends the contact model res.partner. When a contact's email is written, it checks whether the person making the change belongs to the portal user group (base.group_portal). Only in that case does it look at the linked user accounts (user_ids) and, if one of them has a login equal to the previous email, it updates that login to the new email.

Key behaviours: - The login is only changed when the email actually changes (old and new values differ). - Only portal users trigger this behaviour; internal users editing contacts are not affected. - Only user accounts whose login matched the old email are updated, so unrelated logins are left untouched. - If the contact has no linked user, or no user login matches the old email, nothing happens.

There are no new menus, screens, buttons or reports. The change happens silently in the background when a portal user saves a new email on their contact details.