This improvement makes it easier for businesses and developers to customize how Belgian CODA bank files are processed in Odoo. Previously, customizing the file parsing required duplicating complex code; now it can be done through cleaner extension methods. This reduces maintenance burden and makes the system more flexible for organizations with specific bank file processing needs.

Before this commit it was very difficult to change the logic of the CODA file parsing, if not copy-pasting `_parse_bank_statement_file` method in `account.journal`.

This update streamlines the appointment booking process for users who are not logged in. The form flow has been simplified to make it easier and faster for guests to schedule appointments without needing to create an account first.

Simplify the form flow for non-logged users.

Task-4154838

Forward-Port-Of: odoo/enterprise#72113
Forward-Port-Of: odoo/enterprise#69942