Producer API

[tbartelmess]

Currently, Kafka-NIO only features a consumer API, a producer API is missing.

The first version of the producer API will be very similar to the Kafka's Java producer API, and won't support transactions.

class KafkaProducer<K, V> {
    struct Configuration {
       enum Acknowledgements {
           case none
           case leaderOnly
           case fullISR
           case custom(Int)
       }
       batchSize: Int
       linger: TimeAmount?
       memory: Int
       keySerializer: Serializer<K>
       valueSerializer: Serializer<V>
    }
    func send(topic: Topic, key: K, value: V) -> EventLoopFuture<Void>
    func flush() -> EventLoopFuture<Void>
}