Add Support for OAuth 2.0 Authorization Code with PKCE Flow

[missourian55]

Description
For SPA & Native apps (public clients) this is the recommended way to implement the Authorization code flow

Implementation ideas
Some of the reference materials I looked into are

https://developer.okta.com/blog/2019/08/22/okta-authjs-pkce

https://dzone.com/articles/securing-web-apps-using-pkce-with-spring-boot

https://www.stefaanlippens.net/oauth-code-flow-pkce.html

[sberyozkin]

Sure, we've been planning to do it even for the confidential clients

[sberyozkin]

@missourian55 I'd like to clarify, we can't do anything around making sure the tokens acquired by the SPA scripts or public clients use PKCE as Quarkus OIDC adapter does not control the code flow for these types of clients. We can only get PKCE applied to the code flow run for Quarkus web-app applications.

[missourian55]

Makes sense to me. Thanks!

[sberyozkin]

Prioritizing on it asap