[FIX] mail: allow to create channel with user in another company

When there is no intersection between the allowed companies of the current user
and the target user, the `with_user` would lead to the company check always
failing.

opw-2197955

addons/mail/models/mail_channel.py

@@ -470,7 +470,10 @@ def _channel_channel_notifications(self, partner_ids):
         for partner in self.env['res.partner'].browse(partner_ids):
             user_id = partner.user_ids and partner.user_ids[0] or False
             if user_id:
-                for channel_info in self.with_user(user_id).channel_info():
+                user_channels = self.with_user(user_id).with_context(
+                    allowed_company_ids=user_id.company_ids.ids
+                )
+                for channel_info in user_channels.channel_info():
                     notifications.append([(self._cr.dbname, 'res.partner', partner.id), channel_info])
         return notifications