RATIONALE
Channel model is a mail.thread enabled model behaving strangely with followers,
notifications and discuss. Its code should however be simplified to be more
self contained and avoid unwanted side effects on other models.
PURPOSE
Remove channel ability to follow records as it mainly adds noise without a lot
of added value. Simplify channel notification flow by using directly members
and not a delegation through a channel self-following trick. Remove followers
being channels and posting with added listeners being channels.
SPECIFICATIONS
As there is no way to add channel-based follower anymore we can remove all
fields and code supporting this feature. Notably we can remove ``channel_id``
field on ``mail.follower`` model as well all code using it, notably compute
methods.
In this commit we also make ``partner_id`` field required as now followers
are always partners. Email, name and active fields are now simple related
fields on the partner.
Code computing data about subscription is also updated and simplified. As
we do not have channels anymore but only partners all custom SQL queries
are now simplified.
JS models for Discuss are also cleaned. Following python change, JS models
are simplified to match the backend models. Channel_id is removed, partner_id
is now required, and various code is updated according to the simplified
model.
Side note: we could probably get rid of specific index on ``partner_id``
field. However we have to ensure we never search for followers without being
in a model / res_id context. This will be done in another cleaning step to
be sure performance are not broken.
LINKS
Task ID-2070632 (main task)
Task ID-2419762 (followup task)
COM PR odoo/odoo#62859
ENT PR odoo/enterprise#15172
UPG PR odoo/upgrade#2005
Thibault Delavallée
4cb1f56aba