This update adds three new fields to invoices generated within the Chorus Pro system: Buyer Reference, Contract Reference, and Purchase Order Reference. These fields ensure invoices comply with Chorus Pro requirements, improving data accuracy and facilitating seamless integration with the Chorus Pro platform.

This commit:
- Add three reference fields to invoice PDF for Chorus Pro compliance: Buyer Reference, Contract Reference, and Purchase Order Reference. These fields appear in the invoice header when set on the invoice.

task-5410836

Forward-Port-Of: odoo/odoo#240494