code: function createActivity({ type = ActivityTypes.Message, recipient, from, conversationId }) {
      const activity = new Activity({ from, recipient, type, id: '' + activityId++ });
      activity.conversation = new ConversationAccount({ id: conversationId });
      return activity;
  }
docs: Utility for creating a new serializable Activity.
  
  @param {ActivityTypes} type The Activity type
  @param {string} to The recipient of the Activity
  @param {string} from The sender of the Activity
  @param {string} conversationId The id of the conversation
  @returns {Activity} The newly created activity