PURPOSE
Purpose of this task is to remove the _onchange_template_id method on composer
model. Split it into editable computed stored fields. It gives a better control
of value generation and avoid having to call the onchange when composer is
invoked in code.
SPECIFICATIONS
Remove onchange as it is not used anymore. All fields have been converted.
Task-2088884 (Mail: Use editable computed stored fields in composer)
Part-of: odoo/odoo#107356
Thibault Delavallée
300ae603d1