code: function constructAppGroupModel(id, lastUpdated, priority, links) {
      var model = {};
      if(id) model.id = id;
      if(lastUpdated) model.lastUpdated = lastUpdated;
      if(priority) model.priority = priority;
      if(links) model.links = links;
  
      return model;
  }
docs: Constructs an object that reflects the structure of an App Group Model
  @method constructAppGroupModel
  @param id                unique key of group
  @param lastUpdated       timestamp when app group was last updated
  @param priority          toggles the assignment between user or group scope
  @param links             discoverable resources related to the app group
  @returns {}              the AppGroupModel object