pub async fn respond(
client: &RestClient,
target_device_id: &str,
peer_pub_b64: &str,
user_master_key_b64: &str,
) -> Result<(), RespondError>Expand description
Build and post an encrypted key bundle for target_device_id.
user_master_key_b64 is the local device’s stored encryption key
(base64url(32-byte AES-256 secret)). peer_pub_b64 comes from
the WS event payload; the relay vouches for its origin.