pub async fn locale(req: Request, next: Next) -> Result<Response>Expand description
Middleware: parse the inbound Accept-Language header and
stash the negotiated locale in the request context. Falls back
to DEFAULT_LOCALE when the header is absent or contains no
valid tag. Never fails — locale negotiation is best-effort by
design, and a missing or malformed header collapses to the
default rather than rejecting the request.