Feature Request: Ability to list unused provider fields

[timvahlbrock]

One of the main advantages Pact is marketed with the ability to identify and remove unused Provider fields. However, currently there is no real way determining unused fields automatically. This should be possible by collecting all provider responses during verification and identifying any of the fields that haven't been used by any of the consumers. Of course this only works if all consumers are verified at once. @YOU54F mentioned there have been requests to store provider responses in the broker, which would make it possible to add this feature to the broker alternatively.