[FIX] sale: add missing SO origins

When an invoice gathers multiple SO, only one SO was specified in the
origin.

opw-653598

addons/sale/sale.py

@@ -304,6 +304,8 @@ class SaleOrder(models.Model):
                     inv_data = order._prepare_invoice()
                     invoice = inv_obj.create(inv_data)
                     invoices[group_key] = invoice
+                elif group_key in invoices and order.name not in invoices[group_key].origin.split(', '):
+                    invoices[group_key].write({'origin': invoices[group_key].origin + ', ' + order.name})
                 if line.qty_to_invoice > 0:
                     line.invoice_line_create(invoices[group_key].id, line.qty_to_invoice)
                 elif line.qty_to_invoice < 0 and final: