code: static String buildCombinedType(String eventType, Optional<String> objectType) {
      return Joiner.on("/").skipNulls().join(eventType, objectType.orNull());
    }
docs: Combines event and object type into a single type string.
  
  @param eventType type or category of the reporting event.
  @param objectType optional type of the object this event applies to.
  @return Combined type string.