code: function startActivity(activityMessage) {
    var activityId = createActivity(activityMessage);
  
    markActivity(activityId);
  
    var activity = getActivity(activityId);
    writeActivity(activityEvents.start, activity);
  
    return activityId;
  }
docs: Create and start a new activity.
  @param {string} activityMessage Message to use for activity.
  @return {number} Activity id.