JupyterHub breaks if the dependency on accounts is removed

The accounts dependency is justified by the default authenticator requiring it. But we may want to change the authenticator and remove the dependency

Start by reviewing the JupyterHub dependency configuration and the default authenticator entry point. Determine what authenticator should replace the current dependency and whether JupyterHub still works without accounts. Done means the intended authenticator and dependency behavior are agreed and the dependency-free setup is verified.

Written by the indexing model from the issue text.