Indicates the "quality of protection" options applied to the response by the server.
The value "auth" indicates authentication;
the value "auth-int" indicates authentication with integrity protection.
The server SHOULD use the same value for the qop parameter in the response as was sent by the client in the corresponding request.
A string to be displayed to users so they know which username and password to use.
This string should contain at least the name of the host performing the authentication and might additionally indicate the collection of users who might have access.
WWW-Authenticate or Proxy-Authenticate
A server-specified string which should be uniquely generated each time a 401 response is made. It is advised that this string be Base64 or hexadecimal data. Specifically, since the string is passed in the header field lines as a quoted string, the double- quote character is not allowed, unless suitably escaped.
A string of data, specified by the server, that SHOULD be returned by the client unchanged in the Authorization header field of subsequent requests with URIs in the same protection space. It is RECOMMENDED that this string be Base64 or hexadecimal data.
OptionalstatusCode: HttpStatusCode
Only support MD5 for now.