HTTP Authentication and Authorization header parsing and generation
HTTP authentication challenge types
HTTP authorization credential types
string_of_challenge challenge converts the challenge to a string
compatible with the HTTP/1.1 wire format for authentication challenges.
For example, a
`Basic challenge with realm
"foo" will be
"Basic realm=foo", which can then be combined
www-authenticate HTTP header and sent back to the
client. There is a helper function Header.add_authorization_req
that does just this.