OIDC Dev UI should support web-app application by recognizing q_session cookie

[sberyozkin]

Description

OIDC Dev UI is implemented as SPA which authenticates to the OIDC provider itself, useful for testing service or hybrid applications by sending them access tokens as bearer tokens but it is of no use for web-app applications where users authenticate to the OIDC provider bypassing SPA - SPA is, currently, in no control.

However, @FroMage has had a nice idea, if DevUI can detect a q_session cookie then it can send to the dev endpoint to request the content inside that cookie - the devendpoint will be able to decrypt it and return ID token JSON representation, as well as the access token one, and then DevUI, instead of offering an option to login to the already authenticated user, will just show the current user name/roles/etc.

It would be great.

CC @FroMage

Implementation ideas

No response

[quarkus-bot]

/cc @cescoffier (devui), @pedroigor (oidc), @phillip-kruger (devui)