This PR fixes several issues with the unread counter: - Notifications being considered as unread messages (which is not the case on the server side which resulted in inconsistencies). - Counter greater than it should be when the last seen message is not loaded. - Messages not marked as read on first thread opening. task-3239957 closes odoo/odoo#116208 Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>