default String originalTopic(String topic) {
        String upstream = upstreamTopic(topic);
        if (upstream == null || upstream.equals(topic)) {
            return topic;
        } else {
            return originalTopic(upstream);
        }
    }
Returns the name of the original topic, which may have been replicated multiple hops.
Returns the topic if it is not a remote topic.
connect/mirror-client/src/main/java/org/apache/kafka/connect/mirror/ReplicationPolicy.java