Render safe option was used with Jinja rendering to tell Jinja that content
was safe and was not expected to be escaped. This was used notably in subject
as characters like ``&`` was escaped in email subject (e.g. `R&D News`).
This is now supported directly by the "inline template" rendering engine that
is used to render text-based templates since Odoo v15 [1]. This option is not
supported by code anymore anyway and leads to nothing.
Task-2088884 (MailComposer: Onchange to editable computed stored)
Task-2710804 (MailThread Api Cleaning)
[1] See odoo/odoo@68182baff4
Prepares Task-2088884 (Mail: Composer Onchange to Editable Computed Stored)
Part-of: odoo/odoo#94660
Thibault Delavallée
8cbac0506c