public void register(KafkaHandler handler) {
        builder.put(handler.getTopic(), handler);
    }
Configuring and initializing a KafkaConsumer client as a dispatcher to delivery Kafka Message to registered handler
by topic.
oap-server/server-fetcher-plugin/kafka-fetcher-plugin/src/main/java/org/apache/skywalking/oap/server/analyzer/agent/kafka/KafkaFetcherHandlerRegister.java