[FWPORT] account_einvoice_generate: add hook for tax's UNECE Due Date Type Code

Author: alexis-via

account_einvoice_generate/models/account_move.py

@@ -31,3 +31,15 @@ def _xml_format_in_pdf_invoice(self):
             return xml_format
         else:
             return False
+
+    def _get_unece_due_date_type_code(self):
+        """account.tax has a selection field 'tax_exigibility' with 2 possible values:
+        'on_invoice' or 'on_payment'.
+        As a consequence, tax exigibility is a property of the invoice line.
+        But, in real life (at least in France), tax exigibility is a property
+        of the invoice, not the invoice line!
+        This method is a hook to get the UNECE due date type code from the invoice
+        instead of the tax. If it returns None, Odoo will get it from the tax.
+        """
+        self.ensure_one()
+        return None