A guard implementation which supports HTTP header-based authentication schemes.
If no Authorization header is supplied, an anonymous login will
be attempted by using a Anonymous
credentials object. If such a header is supplied and does not contain
allowed credentials, or if anonymous login is denied, a 401 will be sent in
the response along with WWW-Authenticate headers for each of the
allowed authentication schemes.
| Class | UnauthorizedResource | Simple IResource to escape Resource dispatch |