Password checks a username and password against a backing authentication store and returns information about the user and true if successful, false if not successful, or an error if the username and password could not be checked.

Request attempts to extract authentication information from a request and returns information about the current user and true if successful, false if not successful, or an error if the request could not be checked.

Token checks a string value against a backing authentication store and returns information about the current user and true if successful, false if not successful, or an error if the token could not be checked.

PasswordFunc is a function that implements the Password interface.

RequestFunc is a function that implements the Request interface.

TokenFunc is a function that implements the Token interface.