This change updates how Odoo handles unsaved records while users edit forms, making related field updates more consistent and reducing special-case behavior behind the scenes. It affects several business areas such as accounting, HR leave, mail, manufacturing, products, and website events, helping prevent errors during on-screen changes before records are saved.

Using new records in onchange() simplifies code: the environment flag `in_onchange` is gone, and all special cases correspond to new records. The expression `record._origin` is now available on *all* records, and returns the *actual* record corresponding to `record`.