KIP-160 — Augment KStream.print(), KStream.writeAsText() to allow users pass in extra parameters in the printed string

Accepted Kafka 1.0 Streams

KIP-160 adds overloads to `KStream.print()` and `KStream.writeAsText()` that accept a `KeyValueMapper<K, V, String>` so callers can produce custom-formatted output strings instead of the fixed `[key, value]` default. The hardcoded format prevents users from emitting contextually useful representations (e.g. including a timestamp prefix or field projection) without forking Streams internals.

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