[IMP] mail: support custom x_active field

An override of toggle_active was present to ensure that activities
would be removed before archiving records; this commit adapts this
mechanism to take custom active fields into account, since they are
now supported at ORM-level by getting the active field through the
`_active_name` model attribute instead of blindly using the `active`
hard-coded field that was used until now..

closes odoo/odoo#40109

Signed-off-by: Damien Bouvy (dbo) <dbo@odoo.com>

addons/mail/models/mail_activity.py

@@ -701,7 +701,7 @@ class MailActivityMixin(models.AbstractModel):
         """ Before archiving the record we should also remove its ongoing
         activities. Otherwise they stay in the systray and concerning archived
         records it makes no sense. """
-        record_to_deactivate = self.filtered(lambda rec: rec.active)
+        record_to_deactivate = self.filtered(lambda rec: rec[rec._active_name])
         if record_to_deactivate:
             # use a sudo to bypass every access rights; all activities should be removed
             self.env['mail.activity'].sudo().search([