Add control of per-environment active/inactive state to feature flags
Problem to solve
It is normal in a feature flag workflow to have different states on a per-environment basis; production may have a feature off still, for example, but it may be on in a staging environment.
It needs to be possible, for all environments, to be able to set the on/off status for a feature flag.
Because there can be many review environments, we will initially limit the per-environment configuration option to be for only protected environments. Non-protected environments have a single default value that applies to all of them.
What does success look like, and how can we measure that?
(If no way to measure success, link to an issue that will implement a way to measure this)