sendAsync
abstract fun <Req> sendAsync(target: Target, reqSerde: Serde<Req>, req: Req, @Nullable delay: @Nullable Duration, options: RequestOptions): CompletableFuture<SendResponse>
open fun <Req> sendAsync(target: Target, reqSerde: Serde<Req>, req: Req, @Nullable delay: @Nullable Duration): CompletableFuture<SendResponse>
open fun <Req> sendAsync(target: Target, reqSerde: Serde<Req>, req: Req): CompletableFuture<SendResponse>