code: function _addEntityIdentifier(entity, obj) {
      if (entity.constructor === EVT.Entity.Product) {
        obj.product = entity.id;
      } else if (entity.constructor === EVT.Entity.Thng) {
        obj.thng = entity.id;
      } else if (entity.constructor === EVT.Entity.Collection) {
        obj.collection = entity.id;
      }
  
      return obj;
    }
docs: Add the given entity identifier to an object (params or data).