Second Level Cache

Adds caching with minimal code changes, such as adding `second_level_cache expires_in: 1.week` to models, seamlessly fitting into existing Rails workflows.

Write-through caching ensures caches are updated on object saves and deletes, and model schema versioning auto-expires caches when columns change, maintaining consistency.

Allows fetching records by unique keys like nick_name or slugs using `fetch_by_uniq_keys`, eliminating database hits for common lookups.

Optimizes eager loading by transforming IN queries into Rails.cache.multi_read operations, reducing database load for associations as demonstrated in the README example.

Delays cache writes until after transaction commits, preventing stale cache data during atomic operations, as noted in the 'Notice' section.