Abstract role for authentication implementations.

There are multiple different ways one could authenticate against an API, a data store, etc. For example, there is the "basic auth" of a username + password pair. Then there is an OAuth token and secret. The point of this interface is to abstract these implementations.

Each implementation has it's own version of initialization.

$bool = $auth->wrap_http_request($request)

Given a HTTP::Request object, wrap that object in authentication info and return success (1). If there are problems, this returns false (0). The request object is modified by this call.

$string = $auth->username();

Return a username.