In the case of auth methods, we should have a "did you mean..." error message in case of invalid auth method

[shreyb]

Nova had a case recently where they set all user auth methods to tokens using the ENV: JOBSUB_AUTH_METHODS=tokens. That's a typo - the value should be token. But jobsub just complains about an invalid auth method, rather than give a helpful message.

For some finite set of wrong auth methods, like "tokens, proxies, Token, Proxy", etc., we could print a warning message telling the user what the correct strings are.

It's also remarkably easy for a user to use JOBSUB_AUTH_METHOD instead of JOBSUB_AUTH_METHODS. We should probably support both ENVs and have them do the same thing.