Following request #31117, we now have an Option type to represent the possible absence of a value. In the artifact modal, there are several good candidates for this type:

1. CurrentArtifactIdentifier only has a value when the modal is editing an existing artifact (not creating a new one).
2. ParentArtifactIdentifier only has a value when creating a new artifact and the calling code supplied a specific parameter (planning view, when creating tasks)
3. LinkableNumber when entering a number in the link-selector search field of the artifact links field. If it matches the Current Artifact Identifier (you can't link an artifact to itself) or if it's not a number, it has no value.
4. And probably more...

For all these cases, we have represented the absence of value by Value | null. It would be clearer with Option.