Constant UNAUTHENTICATED 

pub const UNAUTHENTICATED: &'static str;

The one message every failed envelope verification carries (ADR 0006 §10): the peer must never learn which check failed. A malformed body, an unknown kid, a disallowed algorithm, a bad signature, a stale iat and a replayed cti all produce CratestackError::Unauthorized with this text, byte for byte.

Moved here from cratestack-cose (which re-exports it) so the axum envelope layer can answer with it without depending on a COSE crate.