Monitoring API #181
Description
Create a new monitoring API in the C interface to the library. Potentially it should just return a JSON string that is an object with arbitrary monitoring statistics.
At the minimum, we should track statistics per-issuer (time spent per issuer, successful validations, unsuccessful validations, expirations, etc). For failed issuer lookup, we should make sure to avoid resource exhaustion DDoS attacks given attackers can generate an arbitrary number of issuers.