[FIX] auth_signup: Not possible to send message in a task from the portal
[FIX] auth_signup: Not possible to send message in a task from the portal

Steps to reproduce:
- Let's consider the portal user Pu, the project Pr and the task Ta
- Add Pu as a follower of Pr
- Log as Pu and open Ta
- Try to post a message

Bug:

An access error was raised due to the rule "res_partner: portal/public: read
access on my commercial partner".

opw:2070320

closes odoo/odoo#36960

Signed-off-by: Simon Goffin (sig) <b3ed2cf313e7546085c3c50622143ff31e467d23@openerp.com>

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo