Warning

These lines of code may be partially or fully hallucinations, and have not been reviwed by a professional dev.

Summary

• Embed relay hints into outgoing DM rumors so each p tag now carries the receiver’s preferred relay URL.
• Added a unit test that confirms relay hints are preserved when rewriting rumor tags.

Problem

DM rumors were emitted with bare ["p", ""] tags, violating NIP‑17 guidance and forcing receivers to guess which relay to query.

Solution

Look up each participant’s messaging relays before gift-wrapping, stash them in a cache, and rewrite the rumor’s p tags with the first available relay hint. A focused unit test verifies the rewrite.

Benefits

• Aligns with the spec so receivers can fetch DMs directly from the hinted relay.
• Improves interoperability with other clients that expect per-recipient hints.

Tradeoffs

• Only the first relay per recipient is included (nostr TagStandard::PublicKey currently allows one hint).
• Adds an extra tags clone per send, negligible at typical DM sizes.

Testing

• cargo check -p coop
• cargo test -p registry -- tests::updates_public_key_tag_with_relay_hint
• Manual: RUST_LOG=registry=debug cargo run, send a DM, and confirm the log shows DEBUG registry::room: Sending DM rumor tags:
  [["p","","wss://…"]].