in src/it/scala/com/gu/kinesis/KinesisTestComponents.scala [99:103]
protected def bootstrapProducer(keyCount: Int)(implicit config: TestStreamConfig): RunnableGraph[UniqueKillSwitch] = {
messageSource(keyCount, messageIntervalPerKey = 1.second, bootstrapKeyPrefix)
.viaMat(KillSwitches.single)(Keep.right)
.to(producerSink)
}