[FIX] im_livechat: livechat rating computes well
[FIX] im_livechat: livechat rating computes well

Open a livechat session between a visitor and a user
That is, open the / controller as public user, and click,
on the bottom right corner, on "Have a question ? Chat with us."
Exchange at least one message to open the session

From the visitor side, close the window. There is a proposal to rate the discussion
Assign either the green face or the yellow one
(The red one is a bit trickier)

Now, on the user side, check the list view of LiveChat sessions

Before this commit, the rating of those sessions were 0
This is because:
The rating.rating < Many2One > mail.channel link is not a foreign key
(rather, it is composed by char::res_model; Integer::res_id)
and doesn't make the reciprocal field recompute, which in turn doesn't make
our relevant field compute

After this commit, the last_rating field field is recomputed and appear in the list view

OPW 2052964

closes odoo/odoo#35830

Signed-off-by: Lucas Perais (lpe) <42d29efea96f3992aa24782120ec2948e42548fa@odoo.com>
ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo