follow-up on 28b3156bc6 which broke
when tokenFile was left empty.
Making both options nullable also allows us to provide a more meaningful
error message when neither authentication method is configured.
Use new command-line flags of release 0.3.0 and always answer with the
expected XML in the VM test instead of using a test-specific fixed path.
Co-authored-by: ajs124 <git@ajs124.de>