def for_role(*roles)
      sql = with_role_sql(roles) || ''
      sql += ' OR ' if sql.present?
      sql += "(#{self.table_name}.roles_mask = 0) OR (#{self.table_name}.roles_mask IS NULL)"
      where(sql)
    end
def for_role(*roles)
      sql = with_role_sql(roles) || ''
      sql += ' OR ' if sql.present?
      sql += "(#{self.table_name}.roles_mask = 0) OR (#{self.table_name}.roles_mask IS NULL)"
      where(sql)
    end
Returns all records which have been assigned any of the given roles, as well as any record with no role assigned