What's the recommended way to define an external service? Is there a set of interfaces that define life-cycle for an extension? I see CacheService[1] but it is currently defined as internal.
[1] https://raw.githubusercontent.com/apache/geode/880a9d614d1ac2418c5bace4fdbb8e255ab8e3dd/geode-core/src/main/java/org/apache/geode/internal/cache/CacheService.java
