[IMP] mail, *: clean up message component by introducing view model

[seb-odoo]

• = hr, hr_holidays, sms, snailmail, website_livechat

Message model incorrectly contained data related to a specific component (only
one) even though there can be multiple message components per message model.

This cascaded to adapting related component/models to the same principle.

[robodoo]

Pull request status dashboard.

[seb-odoo]

Hello @odoo/rd-security could you please validate this change?

Reason: there is a rename on the flagged line

Side question: shouldn't we be able to do it ourselves for trivial cases?

[mart-e]

Side question: shouldn't we be able to do it ourselves for trivial cases?

I don't mind if we give more people have the override rights but there is no such things as a trivial case (well maybe writting innerHTML in a code comment is a trivial case).
For instance, here, the renaming of an existing variable is not a valid enough reason for override. It's an occasion for a double check and ensure the content is still trust-worthy and not injectable (e.g. if we modified the computation of prettyBody in the meantime and make it unsafe by accident).