Idempotent swap slot operation to support swapping via ARM template deployments
This would simplify deployment governance (no need for an out-of-band swap operation when doing a deployment). Ideally the API would look something like:
"slot": "staging", // The slot to look at
"type": "oldest|newest" // Whether the oldest or newest bits between the "active" and the specified slot should be taken. This allows our operation to be idempotent and predictable.