The requirement of partner_id was put long ago because send_to_shipper() method requires it. But if you look into the python code, you see in _send_confirmation_email() method that the requirement to enter into send_to_shipper() is `integration_level == 'rate_and_ship'` instead of `delivery_type not in ['fixed', 'base_on_rule']`. It means that, with this change, if we have a `delivery_type not in ['fixed', 'base_on_rule']`, we should be able to validate the picking without partner if we have `integration_level == 'rate'`.
closesodoo/odoo#136149
Signed-off-by: William Henrotin (whe) <whe@odoo.com>
Miquel Raïch
2129dcb288