slug property
Slug is the product handle the image was attached to. It IS the asset's design field — that equality is the whole join between the studio and the catalog, which is why an asset with no design produces no storefront result at all.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? slug;