void sendIdempotentProducerResponse(int expectedSequence, TopicPartition tp, Errors responseError, long responseOffset, long logStartOffset) {
        sendIdempotentProducerResponse(-1, expectedSequence, tp, responseError, responseOffset, logStartOffset);
    }
Tests the code path where the target node to send FindCoordinator or InitProducerId
is not ready.
clients/src/test/java/org/apache/kafka/clients/producer/internals/SenderTest.java