Behaviour for final generated-image caches.
Configure an implementation with config :og_ex, cache: MyCache. Cache keys
are internal terms and may change between OgEx versions; implementations
should treat them as opaque.
Summary
Callbacks
Retrieves an encoded image for a renderer cache key.
Stores a complete encoded image under a renderer cache key.
Callbacks
Retrieves an encoded image for a renderer cache key.
Returns {:ok, image} when the key exists and :error when it is absent,
following the convention established by Map.fetch/2.
Stores a complete encoded image under a renderer cache key.
Failed or partial renders are never passed to this callback.