I’ve had to do this for several JDBC connectors. Usually, just add to your account aggregation operations something like ‘DB Account’ as “Entitlement” so that every aggregated account has the entitlement called DB Account. Then you need to have either a JDBCProvision rule or use the Provisioning Query Settings (pictured):
You will still need to assign the “DB Account” entitlement, or whatever you end up calling it, in order to generate a provisioning plan.