use Kafka Producer Consumer interfaces

[arun0009]

Use Kafka Producer, Consumer interfaces as types where appropriate instead of using implementation types. Resolves #244

[Avasil]

Thank you, I have just one comment!

I will release a snapshot if you'd like to try it out before including it in the official release

[Avasil]

I think producerRef should be taken lazily, or as a Task / Coeval.
The implementation can close ApacheProducer and that should be only done by the producer (creator) of the resource.

[arun0009]

Is this what you mean?

  /** Builds a [[KafkaProducer]] instance with provided Apache Producer. */
  def apply[K, V](config: KafkaProducerConfig, sc: Scheduler, producer: Coeval[ApacheProducer[K, V]])(
    implicit K: Serializer[K],
    V: Serializer[V]): KafkaProducer[K, V] = {
    lazy val producerRef = producer.value()
    new Implementation[K, V](config, sc, producerRef)
  }

[Avasil]

Yes, although Implementation would have to use Coeval as well, otherwise it will initialize right away

[arun0009]

Ok, pushed a commit that uses Coeval producer.

[arun0009]

@Avasil - Just to let you know, we were able to use the snapshot jar which includes this PR and we were able to wrap Tracing as expected.

[Avasil]

@arun0009 That's awesome, thanks for the update :)