Remove guard.history after setting in cache

[CalebCourier]

Currently, if guards are loaded from a config, their history is held in memory. We already have an endpoint for fetching history for a specific guard call that we use when communicating between the client and the server. This cache applies a 5 minute TTL on each history entry as well as limits the cache to only 50 entries to prevent memory leaks.

However, since the guards are now objects kept in memory in the config rather than constructed JIT from the database, history is still being held on the guard instances. We should delete/reset Guard.history to an empty Stack once a /validate call is done. We should also investigate other means of dumping/persisting history somewhere else via a logging API.