[FIX] calendar: allow search on message_ids
[FIX] calendar: allow search on message_ids

When fixing calendar search for recurring events we assumed that
no autojoin field will be used in this search.

The filter unread messages is based on message_ids from mail thread.
The solution here is to redefine this field in calendar to remove the autojoin.

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