code: public function decodeMessageRef($value, Field $field)
      {
          return new MessageRef(
              SchemaCurie::fromString($value['curie']['S']),
              $value['id']['S'],
              isset($value['tag']['NULL']) ? null : $value['tag']['S']
          );
      }
docs: @param mixed $value
  @param Field $field
  
  @return MessageRef