The restore_cached_data plugin re-extracts metadata
when assigning already cached files, i.e. when the attachment has been retained
on validation errors or assigned from a direct upload. In both cases you may
want to re-extract metadata on the server side, mainly to prevent tempering,
but also in case of direct uploads to obtain metadata that couldn't be
extracted on the client side.
plugin :restore_cached_dataIt uses the refresh_metadata plugin to re-extract metadata.