I just added support for NIP-70 in noteguard, so if you want to add NIP-70 support to your strfry relay its super easy now:
https://github.com/damus-io/noteguard?tab=readme-ov-file#noteguard nostr:note1qzpqsjq6nq0vq0a6ckylvl7yd69y4h7260z3l4yysh9x5kr37ejqjxq3qh