My proposal:

First step: Keycloak configuration

UnifiedPush Server uses Keycloak as an authentication and user management endpoint. You can either use a default instance that comes with UnifiedPush Server installation or you choose to select an existing or a standalone Keycloak installation (so you can use it as an authentication backend for more applications).

Default - A bundled Keycloak instance will be used as authentication backend
Custom - Use an existing or a standalone Keycloak instance (by providing its URL)