Cache OS: Store and retrieve cached data in files

This class can be used to store and retrieve cached data in files.

It can check if a cache file with a given key exists and retrieve its data.

The class can optionally check if the cache file was created before a given expiry time has passed.

If the cache file does not exist or expired, the class can store new data in the cache file.

The class may also delete cache files with a given key or delete all cache files in the cache directory or sub-directory.