get https://api-demo.single-invoice.co/v2/transactor//externalids
Returns information about a company specified by an external service type and an external service ID
This method allows you to retrieve the External IDs that are linked to a specific Single-Invoice.co company.
It will return an array of items including the ID, service code, and country code for each linked External ID.
An External ID is typically the unique ID in some sort of company registry - for example, French companies each have a unique SIREN code.
Note that a list of the supported service codes is available with the Services Listing endpoint.