[IMP] mail: do not send email on join/leave mailing channel

Before this commit, when a user joined, left, or was invited to a
channel with "Send by email", it sent an email notification to every
member.

This commit disables email notification on subscribe/unsubscribe on
a channel, while still showing messages on join/leave.

Task-Id 2003281

closes odoo/odoo#35142

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/models/mail_channel.py

@@ -781,7 +781,7 @@ class Channel(models.Model):
                     }
                 else:
                     notification = _('<div class="o_mail_notification">joined <a href="#" class="o_channel_redirect" data-oe-id="%s">#%s</a></div>') % (channel.id, channel.name,)
-                self.message_post(body=notification, message_type="notification", subtype_xmlid="mail.mt_comment", author_id=partner.id)
+                self.message_post(body=notification, message_type="notification", subtype_xmlid="mail.mt_comment", author_id=partner.id, notify_by_email=False)
 
         # broadcast the channel header to the added partner
         self._broadcast(partner_ids)

addons/mail/models/mail_thread.py

@@ -2100,7 +2100,7 @@ class MailThread(models.AbstractModel):
     # Notification API
     # ------------------------------------------------------
 
-    def _notify_thread(self, message, msg_vals=False, **kwargs):
+    def _notify_thread(self, message, msg_vals=False, notify_by_email=True, **kwargs):
         """ Main notification method. This method basically does two things
 
          * call ``_notify_compute_recipients`` that computes recipients to
@@ -2131,7 +2131,8 @@ class MailThread(models.AbstractModel):
             message_values['channel_ids'] = [(6, 0, [r['id'] for r in rdata['channels']])]
 
         self._notify_record_by_inbox(message, rdata, msg_vals=msg_vals, **kwargs)
-        self._notify_record_by_email(message, rdata, msg_vals=msg_vals, **kwargs)
+        if notify_by_email:
+            self._notify_record_by_email(message, rdata, msg_vals=msg_vals, **kwargs)
 
         return rdata