RATIONALE
Naming conventions
* content = core message / subject (+ other fields);
* email layout = layouting applied to messages when sent to recipients who
receive notifications by email e.g. access button, ...;
* comment mode / mailing mode: composer main composition mode: posting on
record(s) / sending a mailing on records;
Content situation when using a template on the composer
* comment, monorecord mode: choose a template, content is rendered directly
from template side according to 'lang' field definition -> ok;
* comment, multirecord mode / mailing mode: choose a template, content is
the raw content. At post / send, content is rendered on composer side.
As composer is not translated -> no translation -> ko;
PURPOSE
Take translations from template when composer content is the same as the
template one to benefits from their translations.
SPECIFICATIONS
When rendering some fields fetching translations can be complicated. Indeed
when using a template the translation is stored on template model while the
rendering is done on composer model. Translations are therefore not fetched
as fields of the composer record itself are not translated. It is a transient
record, not something people translate manually like templates.
As translations are not stored in a table anymore we can't really fetch
translations, except from using directly the template field. In this commit
we therefore do the rendering based on template value instead of composer
value when they are considered as equal and if a translation is asked either
through 'compute_lang' of 'force_lang'. This allows to fetch template
translations instead of composer translations.
If the composer content has been modified compared to the template we keep
the old behavior, which means probably no translations. Let us hope editor
does not mess too much with html content.
EXAMPLE
A user in english uses a template on a lead whose customer is in spanish
with a follower being in german. Template lang is customer's lang:
* content is translated into spanish (customer's lang);
Concerning layout (to be fixed in next commits):
* layout is partly translated into spanish (customer's lang) if coming from
form view, otherwise is in english (current user's lang);
LINKS
Task-3046371 (Mail: Better Language Support in Composer)
Part-of: odoo/odoo#106177
Thibault Delavallée
110d86f504