Returns the WWW-Authenticate challenges a 401 offers, in this service's order of preference: Bearer, then Basic when offered, then GNAP when offered and a request is given (its as_uri needs the request's base).
WWW-Authenticate
as_uri
Optional
the request, when there is one
the challenge strings
Returns the
WWW-Authenticatechallenges a 401 offers, in this service's order of preference: Bearer, then Basic when offered, then GNAP when offered and a request is given (itsas_urineeds the request's base).