feat: OAuth2 support

[rkravinder05]

Add OAuth 2.0 Token Authentication Support

What's Added

• OAuth 2.0 token-based authentication for Snowflake target
• External token management approach - users provide pre-generated access tokens
• Added a test

Why External Token Management?

Users generate OAuth tokens outside of Meltano. This approach provides:

• User Control: Full autonomy over token generation and lifecycle
• Security: No OAuth flow complexity in the target itself

Configuration

target_snowflake:
  config:
    account: my_account
    user: my_user
    warehouse: my_warehouse
    role: my_role
    database: my_database
    oauth_access_token: "${SNOWFLAKE_OAUTH_TOKEN}"

[edgarrmondragon]

Thanks @rkravinder05, just one question about where token should be passed to the connector?

Links

• https://docs.snowflake.com/en/developer-guide/python-connector/python-connector-connect#connecting-with-oauth

[edgarrmondragon]

We're passing the token in two places: here and in line 280. We probably only need one, can you confirm?