Odoo Customer Peppol EndpointID in Peppol BIS Billing 3.0

Question

We need to generate e-invoices in Odoo that comply with the Peppol BIS Billing 3.0 standard that is used in Luxembourg for e-factoration. When we activate the Peppol BIS Billing 3.0 Protocol under Accounting > Configuration > Journals > Customer Invoices we get in addition to the generated PDF invoive the XML representation of the corresponding invoice as attachment (when send by mail).

When the customer has a valid VAT ID (in Luxembourg the format is: LU12345678) and this is indicated in the customers dataset, everything is ok. The generated ...ubl_bis3.xml uses the VAT ID to generate the Peppol EndpointID like this:

...
<cac:AccountingCustomerParty>
<cac:Party>
<cbc:EndpointID schemeID="9938">LU12345678</cbc:EndpointID>
...

Beside the VAT ID a lot of administrations and organisations use other identifiers (social immatriculation number) for their endpoint ID like e.g. 9938:20225000299 for the geological service. Since Odoo doesn't accept these identifiers as valid VAT ID's (which is correct) we don't know how to add this information to specific customers. Odoo lacks a specific field to add a Peppol endpoint ID, that would automatically be evaluated and used in the generated Peppol BIS Billing 3.0. XML.

We did not find a module, that offers this functionality which we find strange, since this should be a common problem, not only specific for Luxembourg. Do we miss something?

Otherwise the only way would be to write a new module that adds a new field (Peppol ID) to the database, the customers form and to the qweb generating the Peppol BIS Billing 3.0. XML file.

Doesn't this already exist somewhere??