OpenID Connect single logout support

[skyflyer]

Summary

OpenID Connect Session specification defines RP-Initiated logout, which, upon successful termination of user's session on the RP redirects the end-user (client) to the OP (OpenID Provider).

It would be great if OAuth2 infrastructure dealing with OpenID Connect would be able to support this use case as well.

Additionally, it would be great if configuration of OpenID Connect provider could be done via a single property, specifying only the "well known" configuration endpoint, such as https://<provider-fqdn>/.well-known/openid-configuration

Expected Behavior

To be able to configure the end-session-uri property of the spring.security.oauth2.client.provider in the application.yml (or application.properties or through code) and have the appropriate logout handler redirect to that endpoint after the logout.

[jgrandja]

@skyflyer This issue has already been logged #5350

[skyflyer]

My search fu wasn't working, apparently. Sorry about the duplicate.