You can integrate with an external billing system to fetch payment details, bills, usage metrics and other data stored in the external system.
Host an API suite
You can host an API suite in any third-party system. If you use MuleSoft, see Set Up MuleSoft for Integration
Create Named Credentials
To connect with Self-Service Portal, you must share the details of your external system via Named Credentials.
Create an Integration Definition
Then, create an Apex Defined integration definition. APIs work with integration definitions to perform operations in both Salesforce and the external system. Select the Apex Class eucommon.EUIntegrationHandler.
Note The EUIntegrationHandler Apex Class has the default
named credential set to EU_Named_Credential. Replace the default value with the named
credentials in your system.