KIP-825 — introduce a new API to control when aggregated results are produced

Accepted Kafka 3.2 Streams

Adds an EmitStrategy API to TimeWindowedKStream and SessionWindowedKStream with ON_WINDOW_CLOSE (emit only the final result when the window closes) and ON_WINDOW_UPDATE (current behavior: emit for every record). The existing suppress(Suppressed.untilWindowCloses()) approach uses a redundant in-memory buffer with its own changelog topic, adding CPU, memory, disk, and operational overhead to achieve what is logically a windowing-level concern.

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