Documentation can be found here https://developer.atlassian.com/server/framework/atlassian-sdk/audit/
This describes the “new” API introduced with Jira 8 Improvements to your Jira 8.8 audit log - Atlassian Developer Blog and a migration guide guide here Migrating to the new Jira audit log Java API
And here some guide New auditing features coming to Server/Data Center - What you need to know in Developer Community