[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) <lpe@odoo.com>

addons/im_livechat/controllers/main.py

@@ -80,7 +80,6 @@ class LivechatController(http.Controller):
     @http.route('/im_livechat/feedback', type='json', auth='public')
     def feedback(self, uuid, rate, reason=None, **kwargs):
         Channel = request.env['mail.channel']
-        Rating = request.env['rating.rating']
         channel = Channel.sudo().search([('uuid', '=', uuid)], limit=1)
         if channel:
             # limit the creation : only ONE rating per session
@@ -101,7 +100,11 @@ class LivechatController(http.Controller):
                 # if logged in user, set its partner on rating
                 values['partner_id'] = request.env.user.partner_id.id if request.session.uid else False
                 # create the rating
-                rating = Rating.sudo().create(values)
+
+                channel.write({
+                    'rating_ids': [(0, False, values)]
+                })
+                rating = channel.rating_ids[0]
             else:
                 rating = channel.rating_ids[0]
                 rating.write(values)