If a visitor has access to a task through access_token, he should have
access to the task attachments. He already see the list of attachment
and their name, but since the task access_token is not propagated to the
attachment he doesn't have the rights to see them.
In this PR, we generate the attachments access_token and provide them to
the user that is viewing a task with an access_token.
opw-2125252
closes#41881closesodoo/odoo#42121
X-original-commit: e7984c4968cde2019edca6c767d2acce2f7fe3f4
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>