Notify when Redis Transaction got committed

[BernhardBln]

Is your feature request related to a problem? Please describe.
In @RedisTransactional projections, we need to know when the transaction got committed, in order to rebuild some caches.

Describe the solution you'd like
I'd like to have an interface that I can implement in @RedisTransactional annotated projections, that gives me onCommit() and onRollback() handlers.

Describe alternatives you've considered
Currently we do this via a subscription on the state bucket, relying on some internal information like the name of the bucket, which is a bit dangerous. Also it requires the server to have a specific notify-keyspace-events configuration for it to work.