PKCE Support for OAuth 2.0

We've added support for OAuth Authorization Code flow with Proof Key for Code Exchange (PKCE).

When creating a new OAuth 2.0 credential with Authorization Code grant type, you'll have the option to select a PKCE code challenge method.

This PKCE code challenge method is optional when creating OAuth credentials. You may select either plain or SHA-256 if you know the OAuth provider you're creating a credential for supports PKCE.

For more information on PKCE, see the RFC.