Feature "Enqueue-Slowdown" (or -Throttling)

[oli-h]

Background: Redis-Memory is limited - therefore queue sizes are limited (queue length multiplied with average queue entry size).
So at some point, EN-queuing suddenly fails (presumed that DE-queuing is not possible for a while)

For stability reasons we should be able to increase backpressure towards EN-queuing process (http- or EventBus-Clients) by delaying a "success enqueue"-reply more and more.
Presuming that the originating EN-queuing process also works sequentially (i.e. it only requests to enqueue a next message when the previous message is successfully enqueued) this simple mechano helps to secure 'our' Redis memory and give us more time (minutes or even hours) to react.

Propose two config options 'per QueueName-pattern':

• enqueueDelayFactorMillis
• enqueueMaxDelayMillis