public static DescribeConfigsResult describeConfigsResult(ConfigResource cr, Config config) {
        KafkaFutureImpl<Config> future = new KafkaFutureImpl<>();
        future.complete(config);
        return new DescribeConfigsResult(Collections.singletonMap(cr, future));
    }
Helper to create a DescribeConfigsResult instance for a given ConfigResource.
DescribeConfigsResult's constructor is only accessible from within the
admin package.
clients/src/test/java/org/apache/kafka/clients/admin/AdminClientTestUtils.java