[FIX] mail: ignore abritrary argument domain for searching channel

We should not trust arbitrary arguments from public method to compose a domain
as it is possible to inject '|' to disable filters and be able to search any
channel (mitigated by access rules).
Create a private method and use a wrapper that ignores the domain.

addons/mail/models/mail_channel.py

@@ -500,8 +500,13 @@ class Channel(models.Model):
         values['channel_private_group'] = self.search([('channel_type', '=', 'channel'), ('public', '=', 'private'), ('channel_partner_ids', 'in', [my_partner_id])]).channel_info()
         return values
 
+    # TODO master: remove domain argument
     @api.model
     def channel_search_to_join(self, name=None, domain=None):
+        return self._channel_search_to_join(name)
+
+    @api.model
+    def _channel_search_to_join(self, name=None, domain=None):
         """ Return the channel info of the channel the current partner can join
             :param name : the name of the researched channels
             :param domain : the base domain of the research