code: public CMAWebhook addTopic(CMAWebhookTopic topic) {
      if (this.topics == null) {
        this.topics = new ArrayList<CMAWebhookTopic>();
      }
  
      this.topics.add(topic);
      return this;
    }
docs: Add a topic this webhook should be triggered on.
  
  @param topic a valid enum value for the trigger reason.
  @return this webhook for chaining