[Feature Request] High availibility / cluster mode

Make it possible to run the server/schedulers multiple times (High availibility) in Kubernets, Swarm,.. but so that jobs do not run twice (do not get executed from other servers)

I saw some other simpler projects using: [Raft](https://github.com/hashicorp/raft) or redis to atomicly lock jobs and distribute configuration.
Also finding other servers/schedulers dynamically with: [go-discover](https://github.com/hashicorp/go-discover )

The issue names no files, tests, or entry points. Begin by mapping how multiple server and scheduler instances currently coordinate jobs, then evaluate the proposed Raft, Redis, and go-discover approaches for Kubernetes or Swarm. Done means a defined high-availability design that prevents duplicate execution and covers configuration and discovery, but implementation details and acceptance tests are unspecified.

Written by the indexing model from the issue text.