Keycloak 22 - last 2.x release version!

As Keycloak 22 comes with a lot of major changes, which are mostly incompatible with prior versions and makes secure, modern and uptodate software development hard, this release will be the last version of the 2.x release branch.
See this blog post here for further details: https://www.keycloak.org/2023/07/keycloak-2200-released.html

Also, there's no guarantee, that this Keycloak testcontainer with version 22 will work properly at all places without errors!

What's Changed besides the above mentioned

• Support metrics by @sventorben in #102