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• Impacted users: Only those who currently rely on passing a ConsumerRebalanceListener, making a call to consumer's topics subscribe interface, and expecting an updated assignment in the callback are impacted. The number of users who rely on this specific use case is expected to be minimal to zero.
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

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