I'd like to be able to make calls like NewUpgrade(cfg) rather than
Upgrade{...}.Prepare, but I wouldn't be able to define a NewUpgrade
function while Config is in the helm package; there would be a circular
import when Plan tried to import run.
Redacting KubeToken may not be sufficient, since it's possible that
someone would put secrets in Values or StringValues. Unilaterally
redacting those seems unhelpful, though, since they may be the very
thing the user is trying to debug. I've settled on redacting the obvious
field without trying to promise that all sensitive data will be hidden.
