Created by: holm
This adds support for custom backoff strategies.
We have a need to do a backoff that adds some jitter to the delay, so we don't get many retries at the exact same time. Instead of hard-coding another strategy, I came up with this solution instead.
I originally wantes to support a custom method directly on the job, but that didn't work as it has to be serialized to json. So I put it on the queue settings instead.