The previous fix (f43c0a5d857d34) wasn't working for images that were already uploaded.
The "metadata" (eg. 'for_*' and 'secure' attributes) were not added to existing uploads.
Also used 'Upload.get_from_url' is the admin/site_setting controller to properly retrieve
an upload from its URL.
Fixed the Upload::URL_REGEX to use the \h (hexadecimal) for the SHA
Follow-up-to: f43c0a5d857d34