Function validate_nip42_authentication 

pub fn validate_nip42_authentication(
    event: &SignedNostrEvent,
    expected_author: &NostrPublicKey,
    challenge: &str,
    relay_url: &str,
    now: u64,
) -> Result<(), SoftchatError>

Validate a NIP-42 authentication event against its exact connection context.

Errors

Returns SoftchatError::InvalidRelayAuthentication for wrong kind, content, challenge, relay, duplicated tags, or timestamp window.