Authenticates request client based on data extracted from the request (see
HeaderAuthenticationParser) as well as looked up from other sources (see Decorator).
Any authentication information obtained from the request and other sources, like
user id, user role, device, etc.
Attempt to authenticate the requester based on the request header.
Attempt to authenticate the requester based on the request header. May return Future[None]
if authentication is skipped, or an error if authentication fails.