Use fspec for event conditions

[jamesnvc]

There is a spec defined for the event conditions, but it currently isn't being used. This is because when the spec is defined, we just know that the params will be a map, but when it's actually invoked, we know that the params will have conformed to the params spec. This means that when the spec generates test cases, it will generate invalid data, which the function is justified in failing for.

Ideally, the conditions spec could dynamically depend on the params spec, so this could be used. However, there would probably have to be some way (possibly metadata) to prevent the function from being generatively tested, since it might be undesirable to have it repeatedly called with test data.