Point of Sale - Prevent closing sessions with stock errors

This module adds a safety check to the Point of Sale closing process. When a user tries to close a session, Odoo first looks at whether that session still has stock transfer errors (for example, a wrong serial or lot number was picked during a sale). If there are errors and the option is not enabled, the session cannot be closed and an error message appears telling the user how many errors exist and which Point of Sale configuration to change.

A new checkbox, 'Allow closing sessions with stock errors', is added to the Point of Sale configuration form, in the inventory location section. By default it is off, so sessions with stock errors are blocked. Turning it on lets users close such sessions anyway.

The module touches the Point of Sale configuration (pos.config) and the Point of Sale session (pos.session). It does not create new menus or reports; the only visible change is the new checkbox in the Point of Sale settings and the blocking message when closing a session.