public EventService lock() {
        lock.lock();
        return this;
    }
Acquire an exclusive lock for this service that prevents anyone else activating or deactivating the service until {@link #unlock()} has been called.
For example, during an import, it may be desirable to stop anyone else re-activating the service, which may cause event unintended resurrection.
<p>
Caller <em>must</em> manually release this lock with {@link #unlock()}, otherwise the EventService will remain stuck in its current state.
manager/api/rest-impl/src/main/java/io/apiman/manager/api/events/EventService.java