Snowflake is retiring user/password authentication, we need to support other methods.

[kajbaf]

User / Password authentication is being deprecated in Snowflake.
You still can accept push notifications for MFA on DUO Mobile, but that's not a practical option for a production system.

The best approach is to use RSA Key-Pair authentication. Here is the documentation on how to set it up. This enables the use of Vanna-AI against Snowflake for production applications.

https://docs.snowflake.com/en/user-guide/key-pair-auth

I have created this PR #959, which enables key-pair authentication to Snowflake, using RSA Private Keys. I appreciate a review.