Implement this interface for any classes that will be called to "start" the authentication process (see method for more details).
at line 48
start(Request $request, AuthenticationException $authException = null)
Returns a response that directs the user to authenticate.
This is called when an anonymous request accesses a resource that requires authentication. The job of this method is to return some response that "helps" the user start into the authentication process.
For a form login, you might redirect to the login page
return new RedirectResponse('/login');
For an API token authentication system, you return a 401 response
return new Response('Auth header required', 401);