* API: introduce ability to watch a VM
* Document ?watch=true for GET /vms/{name} in the OpenAPI specification
* WatchVM: ensure that goroutine is terminated on early return with error
* WatchVM: close channels on goroutine exit
* WatchVM: ensure that we wait for the goroutine after additional barriers
* WatchVM: ignore unexpected keys instead of throwing an error
* WatchVM: perform context-aware writes to a bounded channel
* WatchVM: don't forget to close errCh on goroutine exit too
* WatchVM: don't close readyCh in goroutine to avoid ambiguity
* WatchVM: filter out spurious KVs that signify VM deletion
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