@Override
    public String groupId() {
        return getString(GROUP_ID_CONFIG);
    }
@return the {@link ProducerConfig#TRANSACTIONAL_ID_CONFIG transactional ID} to use for the worker's producer if
using a transactional producer for writes to internal topics such as the config topic.
connect/runtime/src/main/java/org/apache/kafka/connect/runtime/distributed/DistributedConfig.java