This crate contains a file-backed, rotating cache.
The cache should be safe to be accessed from multiple processes at
once.
The cache stores the value at the provided path.
If `keep_old` is >0, the cache will keep up to `keep_old` versions
around which can be queried via the `get_last` method.
The value and its history are stored in the same file,
each generation represented by a single line of JSON.
Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>
