private static String toHexString(byte[] buf) {
        StringBuilder bld = new StringBuilder();
        for (byte b : buf) {
            bld.append(String.format("%02x", b));
        }
        return bld.toString();
    }
ClientCompatibilityTest is invoked by the ducktape test client_compatibility_features_test.py to validate
client behavior when various broker versions are in use.  It runs various client operations and tests whether they
are supported or not.
tools/src/main/java/org/apache/kafka/tools/ClientCompatibilityTest.java