message: add validated flag merge strategy
diff: @@ -28,7 +28,8 @@ const combine = (lhs: MapObject, rhs: MapObject): boolean => {
  valid: (lhs, rhs) => lhs && rhs,
  invalid: (lhs, rhs) => lhs || rhs,
  pending: (lhs, rhs) => lhs || rhs,
  - required: (lhs, rhs) => lhs || rhs
  + required: (lhs, rhs) => lhs || rhs,
  + validated: (lhs, rhs) => lhs && rhs
  };
  return Object.keys(mapper).reduce((flags, flag) => {
  