OidcBackChannelLogoutHandler#logoutUrl not configurable, context path missing from default

[JuergenSimon]

Describe the bug

• When logging out using backchannel-logout, the OidcBackChannelLogoutHandler handles this by generating logout requests to localhost
• The URL generated is http://localhost/logout, but this skips the context path. As a result, this runs into a 404
• Given an application with context path /my-application, I would expect: http://localhost/my-application/logout
• It also seems to fail if the logoutUrl was configured to something else than /logout

To Reproduce

• Set up an application with back-channel logout on keycloak
• Set up keycloak with debug logging
• Log out by terminating the session on key cloak

Expected behavior

• The internally generated log-out does not produce a 404

Proposals

• A) Make the feature aware of the context path
• B) Make the feature respect reconfiguration of logoutUrl
• C) Instead of generating internal requests, use the API to terminate the session

[lmorocz]

It is configurable since 6.2.4, see #14679 (and #14609).

eg. .oidcLogout(lc -> lc.backChannel(c -> c.logoutUri("{baseScheme}://{baseHost}{basePort}{basePath}/logout"))))

[JuergenSimon]

I was still debugging against the 6.2.3 version. I can confirm that with an upgrade to 6.2.4, it works as advertised. Thanks!