With the addition of the new Processor API the newly added FixedKeyProcessorNodeFactory extends the ProcessorNodeFactory class. The ProcessorNodeFactory had a private field Set<String> stateStoreNames initialized to an empty see. The FixedKeyProcessorNodeFactory also had a private field Set<String> stateStoreNames.
When executing InternalTopologyBuilder.build executing the buildProcessorNode method passed any node factory as ProcessorNodeFactory and the method references the stateStoreNames field, it's pointing to the superclass field, which is empty so the corresponding StoreBuilder(s) are never added - causing NPE in the topology.
This PR makes the field protected on the ProcessorNodeFactory class so FixedKeyProcessorNodeFactory inherits it.
The added test fails without this change.
Reviewers: Matthias J. Sax <mjsax@apache.org>, Sophie Blee-Goldman <sophie@confluent.io>, Jorge Esteban Quilcate Otoya <quilcate.jorge@gmail.com>
