[IMP] account: The new draft invoice has the sale order as the source document.

Context:
Source document on invoice created through a credit note with the modify option

Current issue:
create an invoice from a sale order,
validate it,
Create a refund with the modify option
The first invoice is reconciled with the refund
The new draft invoice doesn't have a source document and can't be reached from the SO

Expect result:
The new draft invoice should have the sale order as the source document

addons/account/wizard/account_invoice_refund.py

@@ -98,7 +98,8 @@ class AccountInvoiceRefund(models.TransientModel):
                             'invoice_line_ids': invoice_lines,
                             'tax_line_ids': tax_lines,
                             'date': date,
-                            'name': description
+                            'name': description,
+                            'origin': inv.origin
                         })
                         for field in ('partner_id', 'account_id', 'currency_id',
                                          'payment_term_id', 'journal_id'):