Before this revision, the button "Pay now" on the quotation
in the frond-end was display only if the sale order
was in the state `manual` and that there was not
yet any payment transaction.
The thing is, since the release of 9.0,
the `manual`state no longer exists in `sale.order`,
and the pay now button was therefore never displayed.
From this revision, the condition to display the button
is based on the `invoice_status`, which need to be `to_invoice`,
meaning there is something to pay:
- The sale.order needs to be in states `sale` or `done`
- At least one line has to be invoiced:
- If the product has the `invoice_policy` set to `order`
- or if the product has the 'invoice_policy` set to `delivery`,
and at least one quantity has been delivered.
opw-659931