JWT auth support

[slvrtrn]

Summary

• Support for JWT tokens auth is added (an upcoming feature in ClickHouse Cloud). Closes Add JWT support #270
• Top-level username and password options in the config are now deprecated; the auth object should be used instead.
• Supported via the URL configuration as the access_token param.
• It is possible to override JWT token for a particular request, too.
• The related tests are ignored until we have an instance with JWT support.

The URL config example needs to be updated - maybe later as a follow-up.

Checklist

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[sonarcloud]

Quality Gate passed

Issues
10 New issues
0 Accepted issues

Measures
0 Security Hotspots
82.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[slvrtrn]

82.9% Coverage on New Code

It should increase once the related tests are enabled.

[mshustov]

optional: can we move Auth header calculation logic to a separate function and test separately? It's hard to reason about the flow with a few levels of if

if (isJWTAuth(params?.auth)) {...}
if (this.params.set_basic_auth_header) {
      if (isCredentialsAuth(params?.auth)) { ... } 
      else {...}
}

[mshustov]

It's not the same behavior. With the current change, both params must be provided. I'm okay with it. Let's just add it to the changelog

[slvrtrn]

Previously, it was also required to provide both username and password to override the credentials. The behavior should be exactly the same.