Update documentation for federated authentication
Created by: reqa
For SovereignCloudStack/issues#160
- add Device Authorization Grant
- add Zitadel as an option
Signed-off-by: Arvid Requate requate@univention.de
Created by: reqa
For SovereignCloudStack/issues#160
Signed-off-by: Arvid Requate requate@univention.de