APEX class providing out-of-box implementation:
Use Apex interfaces if you want to completely customize the TMF637 API and only use the Salesforce framework for integrations. The Salesforce framework includes the consent check, permissions and licensing check, and invocation of the REST resource.
You can use the TMFOpenAPIProductInventoryService Apex interface to customize TMF637 API:
By default, no implementation is associated to the interfaces. If you want to add your own implementation of the API handlers, write a class implementing these interfaces and add the details to the interface implementation on the org.