As a bonus, add cross-tab update for current user in chatter.
Part of task-3265211
closesodoo/odoo#120018
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>
This commit focuses on removing all references to discuss.channel from
controllers of mail module.
In preparation of splitting discuss and mail modules.
Part of task-3265211
closesodoo/odoo#119523
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>