feat: allow create/update OAuth2 DB

[betodealmeida]

SUMMARY

This PR is part of the work to add OAuth2 support for Snowflake. When creating the DB we provide only the OAuth2 client information (ID, secret, scope, auth/token URLs), which is not enough to test and validate the connection. We need to allow the DB to be created before the OAuth2 flow, so we can store the access tokens associated with a given DB.

Depends on #30067.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

Added unit tests.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[rtexelm]

LGTM