v2.9.1

1. Added audit log category attribute
   Available categories: announcement, application, auth, challenge, division, dlog, downloads, economy, event, member, poll, system, tracker, user
   Additionally, legacy category is used for all audit log generated before v2.9.1.
2. Added detailed challenge completion record
   NOTE: completed object was changed to record in GET /challenge/{challengeid}; completed (count) attribute was changed to completed_user_count in GET /challenge/list.
3. Fixed error when webhook signature does not exist
4. Fixed error when adding a driver from Trucky webhook when the user exists in the database but does not have driver role