Add check-config command to CLI

[tznind]

@rkm rkm 1 hour ago

What might be useful is a script which you can run after setting everything up which verifies all the specified services and databases etc. are reachable?

e.g. something like ./smi check-config -y foo.yaml

[rkm]

Just thinking that this could have 2 modes -- one which just checks the config is load-able (e.g. by constructing a GlobalOptions object), and another which actually verifies all the specified services are reachable.