class ActiveStorage::Blob

def key

Always refer to blobs using the signed_id or a verified form of the key.
This key is not intended to be revealed directly to the user.
secure-token format from Rails in lower case. So it'll look like: xtapjjcjiudrlk3tmwyjgpuobabd.
Returns the key pointing to the file on the service that's associated with this blob. The key is the 
def key
  # We can't wait until the record is first saved to have a key for it
  self[:key] ||= self.class.generate_unique_secure_token(length: MINIMUM_TOKEN_LENGTH)
end