Current attribute encoder does not support circe style encodind where we can drop nulls.

[aliubymov-playq]

  implicit def optionEncoder[T: D4SAttributeEncoder]: D4SAttributeEncoder[Option[T]] = {
    item: Option[T] =>
      item.map(encode[T]).getOrElse(AttributeValue.builder().nul(true).build())
  }

when we need to

  implicit def optionEncoder[T: D4SAttributeEncoder]: D4SAttributeEncoder[Option[T]] = {
    item: Option[T] =>
      item.map(encode[T]) // expects Optional attribute to not write unnecessary parts
  }

Decoder already supports optional attributes.