Decidim: Verification documents can be downloaded through reusable links

Decidim is a participatory democracy framework. Prior to 0.30.9, from 0.31.0 before 0.31.5, and in 0.32.0.rc1 before 0.32.0.rc2, the identity-document verification admin UI embeds verification_attachment blobs through reusable signed Active Storage disk URLs, allowing anyone who obtains a URL to download the scanned document without an authenticated Decidim session until the signature expires. Verification-document images are rendered with variant_url(...), which produces signed /rails/active_storage/disk/... links instead of routing the file through an authorization-checking controller. Because Decidim configures Active Storage service URLs to remain valid for seven days, the URL itself becomes the credential for that period. The affected files are verification_attachment blobs on Decidim::Authorization, and the admin review pages embed those signed URLs directly into the HTML for pending and confirmation views. This issue is fixed in versions 0.30.9, 0.31.5, and 0.32.0.rc2.