A lot of customer are writting ticket with this issue:
When sending a TEST mail marketing from a campaign, they received a
403 error - Access Denied.
It's happening because the res_id is equal 0 and _valid_unsubscribe_token
from mass mailing controller is expecting it to be <> 0.
The res_id is given by the recipient dropdown of the mass mailing campaign
that allows Odoo to match a known record in Odoo.
opw-2202026
