bearer_auth.nx

bearer_auth.nx -- extract Bearer tokens from Authorization header. RFC 6750. The modern HTTP auth scheme for OAuth 2.0, JWT, API keys, and general \"the client holds a secret and presents it\" flows. Trivial algorithmically but worth isolating behind a helper so callers don't re-invent the case-insensitive prefix parse + whitespace handling every time. Authorization: Bearer eyJhbGciOi... ^^^^^^ ^^^^^^^^^^^^^ scheme token (opaque to HTTP) The token format itself (JWT / opaque random / signed session) is caller's concern -- we just peel the \"Bearer \" prefix. Invariants: BA1 Scheme match is case-insensitive per RFC 7235 §2.1. BA2 Token is returned as (offset, length) into the caller's buffer -- zero-alloc. BA3 Multiple whitespace tolerated between scheme and token (RFC permits 1 or more SP between credentials parts).