Private key based auth

[bmingles]

As an enterprise user, I'd like to be able to authenticate via a private key.

Relevant Docs:

• How to create deephaven authentication keys
• How to connect to Deephaven from another Java program
• Grizzly Python AuthClient.private_key
• Grizzly Python AuthClient.generate_keypair

Notes from conversation with Charles:
Slack - July 30 2:05 PM

The SessionManager.__make_session retrieves an authentication token (I know the JS API can do that), and configures authentication headers and Envoy headers for the udnerlying core session.

This is a Python implementation of the private key authentication:

• https://docs.deephaven.io/pycoreplus/20231218/_modules/deephaven_enterprise/client/auth.html#AuthClient.private_key
• https://docs.deephaven.io/pycoreplus/20240517/_modules/deephaven_enterprise/client/auth.html#AuthClient.private_key
  (use the grizzly source as a reference)

[devinrsmith]

It's not so much the user authenticating via a certificate; it's that the client trusts the servers TLS certificate.

[bmingles]

Ah, I had conflated 2 different issues. I've created #35 to support trusting of certificates. We'll still need this one to support enterprise customers who want to login to their server via a private key.