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If there is a client using older version of the ConsumerGroupHeartbeat RPC , the join flow will still follow the rules which are mentioned in KIP-848#Member ID.

If newer version clients receive an older version heartbeat, they should still adhere to the new behavior, generating the member ID on the client side. This approach is preferred because we believe client-side ID generation is more reliable and scalable than server-side generation, and there are no changes to the fields between the newer and older version RPCs. Ultimately, we aim to phase out server-side member ID generation entirely.

Test Plan

The objective of the test is to ensure that the client using the newer protocol correctly and securely generates a UUID and provides this UUID as the member ID.
At the same time, ensure backward compatibility with older versions of the  ConsumerGroupHeartbeat RPC.
According the objective, we should have the test scenarios as the followings:

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