I would like to implement a custom implementation of AuditStrategy. But at the moment there is no possibility to add your own columns to the AUD-tables. You have to change the database schema with tools like flyway or liquibase and in the AuditStrategy you have to use native queries because manipulating the data-Map does not work for unknown columns.
In the implementation of ValidityAuditStrategy the schema manipulation is hardcoded and not extensible. This should be refactored so that every custom AuditStrategy also contains the schema updates.