Kafka - Record metadata reading and asserting(optional)

> RecordMetadata metadata = producer.send(record).get();

Currently the framework logs the info as below, but it's better to retrieve it in the response if it was available.
```java
LOGGER.info("Record sent with key " + index
+ ", to partition " + metadata.partition()
+ ", with offset " + metadata.offset());
```

e.g.
```json
"assertions": {
"status" : "Ok",
"recordMetadata" : {
"topicPartition" : {
"partition" : 0,
"topic" : "demo-4"
}
}
}

```