Hello devs, I'd like to be able to create my own KTableProcessorSupplier implementation in a Kafka Streams application, but it's currently not possible without the use of reflection due to KTableImpl's valueGetterSupplier & enableSendingOldValues methods being package-local.
Would there be any opposition to a PR to make these methods public? I do understand that implementing interfaces & using classes in an "internals" package are obviously going to be an unstable API. But my current alternative is to swap from DSL to low-level API via a topic, and then swap back, when I can't do something directly with the existing API... and that makes my extensions quite divergent from anything I could feasibly contribute back to the library in the future. :-) Thanks, Mathieu
