helpdesk_mgmt: Email notification goes to wrong recipient on portal ticket creation

[mohamedalibenchiekh]

module: helpdesk_mgmt
version: 16.0

Steps to reproduce

1. Install helpdesk_mgmt module in Odoo 16
2. Configure helpdesk with teams and categories
3. Create a new ticket through the customer portal (/new/ticket)
4. Fill in the form and submit
5. Check email notifications

Current behavior
When a new ticket is created through the portal, the email notification is sent to the customer (partner_id) instead of the assigned user (user_id).

Expected behavior
The email notification should be sent to the assigned user (user_id) when a new ticket is created through the portal, not to the customer.

Additional context
The issue appears to be in the email template configuration where partner_to is set to {{object.partner_id.id}} instead of {{object.user_id.partner_id.id}} in the assignment_email_template.