Thrift backend hardcodes rejectUnauthorized: false — no way to enable TLS certificate verification #462

Body:

Description

The default (Thrift) backend builds its HTTPS agent with certificate verification disabled, and there is no public option to turn it on:

https://github.com/databricks/databricks-sql-nodejs/blob/main/lib/connection/connections/HttpConnection.ts#L68-L77

const httpsAgentOptions: https.AgentOptions = {
  ...this.getAgentDefaultOptions(),
  minVersion: 'TLSv1.2',
  rejectUnauthorized: false,
  ca: this.options.ca,
  cert: this.options.cert,
  key: this.options.key,
};

ca, cert, and key are passed through, but with rejectUnauthorized: false the server certificate is never actually validated, so supplying a CA has no effect on verification. Every connection made through DBSQLClient.connect() on the Thrift path — including OAuth bearer-token traffic — accepts any certificate (self-signed, expired, wrong hostname).

Impact

A misrouted DNS/PrivateLink path or an on-path attacker who can terminate TLS receives bearer-authenticated requests without triggering any client-side error. For a driver that carries workspace credentials this is a significant silent weakening of transport security, and it is not documented on ConnectionOptions.

Expected behavior

Either of:

1. Verify by default — matching Node's own https default, the JDBC/ODBC drivers, and the kernel/SEA backend added in 2.0.0 (which, per its typings, verifies the chain and hostname by default) — with an explicit opt-out for users who need permissive behavior.
2. At minimum, a public opt-in on ConnectionOptions (e.g. the checkServerCertificate / customCaCert options that [SEA-NodeJS] Kernel backend: connection/statement options, TLS & configurable sync/async execution #416 added for the SEA path) so callers can require strict validation on the Thrift path without patching the package.

I understand from the history of #407 that the permissive default was kept deliberately for backwards compatibility, but right now strict verification is not even possible on the Thrift path — that seems worth fixing independently of the default. #197 is related (surfacing agent TLS settings publicly) but does not cover the hardcoded rejectUnauthorized.

Environment

• @databricks/sql 2.0.0 (also present on current main)
• Node.js 22.x

Workaround

We currently patch the package (via patch-package) to set rejectUnauthorized: true, which works because Databricks endpoints present publicly trusted certificates — but a supported option would be much better.