allow checking if user already logged in

[jupyterjazz]

every time hubble.login is called in the finetuner new session is created, overwriting jina_token in config.json

we should allow checking if the user has already logged in, we could have an argument like force which exists in the api part, but not inside the core.

[delgermurun]

@jupyterjazz We released this feature. Please check it out.