chore: Improve Snowflake security auth in CI

[ivergara]

Snowflake is changing the auth flow. Until now, we were using a regular user account, however, those account types will require MFA which is not feasible for CI work.

The alternative I'm using here is to use a key pair.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.28%. Comparing base (73c9e9a) to head (707f672).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #305   +/-   ##
=======================================
  Coverage   91.28%   91.28%           
=======================================
  Files          18       18           
  Lines        2066     2066           
=======================================
  Hits         1886     1886           
  Misses        180      180           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ivergara]

@kklein I'm surprised it worked almost out of the box!

[Copilot]

Pull request overview

This PR migrates Snowflake authentication from password-based to key pair authentication for CI environments, addressing Snowflake's upcoming requirement for MFA on regular user accounts which is not feasible for automated CI workflows.

Key Changes:

• Implemented private key authentication using cryptography library to load and serialize PEM keys
• Updated connection string to remove password parameter and added connect_args for private key
• Replaced SNOWFLAKE_PASSWORD with SNOWFLAKE_PRIVATE_KEY secret in CI workflow

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/integration/conftest.py	Added private key loading and serialization logic, removed password authentication, and updated connection creation to use key pair auth
.github/workflows/ci.yaml	Updated environment variable from SNOWFLAKE_PASSWORD to SNOWFLAKE_PRIVATE_KEY

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[kklein]

LGTM - thanks! :)

[kklein]

@ivergara Would you mind rerunning the pre-commit hooks?