RATIONALE
Currently we can specify email used for notification layouting through context
use in mail composer. It is then propagated to message_post, stored on
mail.message and used to encapsulate emails sent based on posted messages.
SPECIFICATIONS
On template model: rename ``notif_layout`` parameter of ``send_mail`` to
``email_layout_xmlid`` to be coherent with naming used in other parts of the
code. Moreover it better indicates we expect an xml id.
On rating model: rename ``notif_layout`` parameter of ``rating_send_request``
to ``email_layout_xmlid``, for the same reasons as above.
In various wizards: support ``email_layout_xmlid`` context key when no field
is available, notably because this is still done manually in some wizards
like survey invite. Keep a fallback on ``notif_layout`` but remove support of
``custom_layout`` deprecated since quite a long time.
Task-2621326 (Mail: add 'view' button in 'light notification template')
Task-2647302 (Mail: add layout field in composer)
Part-of: odoo/odoo#76418
Thibault Delavallée
f9dbd38720