public String bootstrapServers() {
        return brokers[0].brokerList();
    }
This cluster's `bootstrap.servers` value.  Example: `127.0.0.1:9092`.
<p>
You can use this to tell Kafka producers how to connect to this cluster.
streams/src/test/java/org/apache/kafka/streams/integration/utils/EmbeddedKafkaCluster.java