Is your feature request related to a problem? Please describe.

As I've dug into policies and #658 especially I've discovered that there's no guidance about when a fee/subsidy associated with a policy should be applied to an event. Is it when the event is in violation of the policy, or when it's in compliance? And in the discussion in #658 I think we've made clear that for some rules one way makes more sense, and in others the other way, so I don't think there's one best way to go.

Describe the solution you'd like

Instead of picking one convention or the other I think we could have a rate_applies_when field on policy rules that could have values of violation or compliant that would make this explicit on a per-rule basis.

Is this a breaking change

A breaking change would require consumers or implementors of the API to modify their code for it to continue to function (ex: renaming of a required field or the change in data type of an existing field). A non-breaking change would allow existing code to continue to function (ex: addition of an optional field or the creation of a new optional endpoint).

• No, not breaking

Impacted Spec

For which spec is this feature being requested?

• policy

Describe alternatives you've considered

The alternative I've considered is to pick either compliance or violation as the standard for applying a rate to an event. People would have to structure their rules such that applying the standard would have the desired outcome. I'm not a fan of that, though, because I think some fee rules have to be constructed in counter-intuitive ways when you have to choose one way or the other (see discussion in #658). By letting people specify how rates are meant to be interpreted alongside their rules they can write rules in the ways that make sense to them.

Additional context

N/A.