Controller mixin for authentication-agnostic login: defines the application at runtime to use the authentication method specified in environment config. Intended to be used in tandem with OsfAuthController mixin. Some authentication methods (eg cookies) are not available to third-party applications. This has limited use, since most applications will only need to support one method. It may be useful for ember apps that run inside the OSF, eg to use the standalone dev server, or to offer support for branded apps on third-party domains.