Some of the SOAP modules in SAP S4 HANA Cloud does not have any authentication method in API Hub.
For example, Billing Document - Send Confirmation of Creation with SD Document Reference ( https://api.sap.com/api/CO_SDBIL_ESR_BD_REF_CONF_OUT/overview ) do not have authentication method information in the document.
What authentication method is required to execute such SOAP APIs which do not have any information available in the API Hub document ?