Implement background process to invalidate metadata cache when underlying data is changed

[dmgaldi]

Overview,

Currently, EDA study data is only refreshed in dev/qa environments. When data is refreshed, there is not a mechanism to invalidate out of date cache entries. Since this only happens in non-prod environments, it hasn't been an issue. With the QO, data will be reloaded in production.

• [ ] EDA Common changes (PR https://github.com/VEuPathDB/EdaSubsettingService/issues/99)

Acceptance Criteria

• A background thread periodically checks whether metadata cache is out of sync with source data