Clarify relationship between auth.ClassName.config_name and c.ClassName.config_name

[consideRatio]

This issue is extracted from #564:

But the first part of the documentation (here http://tljh.jupyter.org/en/latest/howto/auth/nativeauth.html#enabling-the-authenticator) use tljh-config to configure jupyterhub and the last part for optionnal features use a config file (here https://native-authenticator.readthedocs.io/en/latest/options.html) it is not clear if the two methods are compatible.

I think in the auth section where we have a passthrough config, where everything set under auth.ClassName.config_name is passed through as if it was c.ClassName.config_name in the documentation of various authenticator projects.

Related

• #705 - An issue about c.ClassName.config_name was configured via tljh-config instead of auth.ClassName.config_name