Cluster High-availability Mode API

[dhellmann]

As we add more deployment topologies for OpenShift, we need a way to
communicate expectations to the operators managing the cluster. This
enhancement describes an API for telling operators how hard they
should work to provide high-availability.

[dhellmann]

/cc @deads2k @wking @eparis @hexfusion @mrunalp @romfreiman

[dhellmann]

/cc @eranco74

[dhellmann]

/cc @lilic

[dhellmann]

/cc @cgwalters

[cgwalters]

Thanks so much for writing this!

[romfreiman]

@danwinship @dcbw @alexanderConstantinescu we should explore using this api for that assisted installer flow in 4.8 (2 nodes that become 3 later on).

[lilic]

cc @simonpasquier @bbrowning for 👀 on the monitoring side of things

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cgwalters, derekwaynecarr, markmc

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[dhellmann]

@dhellmann I had debated if SingleNode should be SingleReplica or just Single , but as it turns out there isn't a great term for the opposite of HA that fits everywhere. The only nit with Node suffix is that we are describing how to schedule pods at the end of the day. I don't think its worth bike-shedding over, but just remarking here if you wanted to update later.

/approve
/lgtm

I could go along with changing it to SingleReplica. I'll send another PR.