[FIX] sale: Payment terms from SO

Let's consider a customer C with payment terms P1 set on it

Steps to reproduce the bug:

- Create a SO for C with payment terms P2
- Confirm the SO and generate the invoice

Bug:

The payment terms on the invoice was P1 instead of P2
This fix allows to keep the same behavior as in 11.0
Introduced by: f1b2d165fb

opw:1905710

closes odoo/odoo#28585

addons/sale/models/sale.py

@@ -563,7 +563,10 @@ class SaleOrder(models.Model):
             # by onchanges, which are not triggered when doing a create.
             invoice.compute_taxes()
             # Idem for partner
+            so_payment_term_id = invoice.payment_term_id.id
             invoice._onchange_partner_id()
+            # To keep the payment terms set on the SO
+            invoice.payment_term_id = so_payment_term_id
             invoice.message_post_with_view('mail.message_origin_link',
                 values={'self': invoice, 'origin': references[invoice]},
                 subtype_id=self.env.ref('mail.mt_note').id)