MR !1919 Added a 404 sentinel to make `errors.Is(err, ErrNotFound` work. This has the side effect that `HasStatusCode(err, 404)` no longer works causing a weird inconsisentcy with checking responses.
Callers can't inspect the response body like they can for other errors.
Proposal is to solve for both `errors.Is(err, ErrNotFound` and `HasStatusCode(err, 404)`