- more aggressive caching of API keys and added cache warmup
- remove direct DB access in APIkey() middleware immediately
- decrease resources usage for test puzzles
- decrease cache collision possibility for cached solved puzzles
- cosmetic improvement in rate limiter and leaky bucket Updater logic
- move user limits check and API key backfill to a separate goroutine
Main reason being otter/v2 release with APIs for sliding expiration.
- added new cache API to use Loader logic from otter/v2 (fetch from DB)
- main direction of work is improving "negative caching" performance
(currently it is still intertwined with the main cache)
- expose new Prometheus metric for cache hit ratio
