This commit is the continuation of task-2948676 which consists of
lightening the Thread model by moving the channel-specific behaviours to
the Channel model.
The changes revolve around the DiscussSidebarCategoryItem model. The
goal is to use channel instead of thread as identifying field for
DiscussSidebarCategoryItem, and to move channel-specific fields involved
in the computes of this model from Thread to Channel.
Changes in this commit include:
+ move `avatarCacheKey` from Thread to Channel
+ move `correspondent`
+ move `correspondentOfDmChat`
+ move `custom_channel_name`
+ move `localMessageUnreadCounter`
+ move `serverMessageUnreadCounter`
+ introduce `Channel/displayName`
+ use channel instead of thread as identifying field for
DiscussSidebarCategoryItem
Part of task-2948676.
closesodoo/odoo#98149
Related: odoo/enterprise#30457
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>