def arel_update
        table = self.class.arel_tables[entity.class.table_name][hydra_attribute.backend_type]
        arel  = table.from(table)
        arel.where(table[:id].eq(id)).compile_update(table[:value] => value, table[:updated_at] => Time.now)
      end
def arel_update
        table = self.class.arel_tables[entity.class.table_name][hydra_attribute.backend_type]
        arel  = table.from(table)
        arel.where(table[:id].eq(id)).compile_update(table[:value] => value, table[:updated_at] => Time.now)
      end
Creates arel update manager

 @return [Arel::UpdateManager]