refresh_metadata plugin allows you to re-extract metadata
from an uploaded file.
UploadedFile#refresh_metadata! method, which calls
Shrine#extract_metadata with the uploaded file opened for
reading, and updates the existing metadata hash with the results.
uploaded_file.refresh_metadata! uploaded_file.metadata # re-extracted metadata
For remote storages this will make an HTTP request to open the file for reading, but only the portion of the file needed for extracting each metadata value will be downloaded.