jupyter extension - allow configuration via env var

[kevyang]

Allow the Pachyderm Jupyter extension address and token to be configured via env var for compatibility with the Determined launcher.

INT-1149

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[msteffen]

Just noting here: we learned during testing today that the token in DEX_TOKEN is an OIDC ID token rather than a Pachyderm token, so it needs to be exchanged for a Pachyderm token during startup.

For reference, cust-eng made a version of that change here

[emmajsadams]

Looks good to me. I investigate the sdk a bit and saw similar code self.auth_token = self.auth.authenticate(id_token=oidc_token) so I think this should work.

I did not pull it down to test though can do if you want me to.

[emmajsadams]

Do we want to add any tests for this new fallback behavior? I think we avoided testing setup_handlers before since it was so simple, but maybe given these branching paths it could be worthwhile now?

[emmajsadams]

For the sake of getting this into the release tomorrow, feel free to handle this in a follow up if you end up thinking it is necessary.

[kevyang]

i will file a ticket for this, i don't think it's very straightforward to toggle the env vars in our testing set up right now.