Skeleton issue: A Reference can have an items Property (ManifestRef, CollectionRef)

[markpbaggett]

According to the validation schema, a Reference cannot have items:

https://github.com/IIIF/presentation-validator/blob/main/schema/iiif_3_0.json#L103

This ensures many things such as Manifests not getting embedded in Collections.

Expected behaviour:

An error is thrown if an instance of a Reference is passed items or items is dropped when this is attempted.

Observed behaviour:

If items is passed, it is kept. For instance, if you use make_manifest() and pass a full manifest, the manifest gets embedded on the collection. For example:

from iiif_prezi3 import Collection

collection = Collection(
    id="https://example.com/collection/1",
)
collection.make_manifest(
    id="https://example.com/collection/1",
    items=[
    {
      "id": "https://iiif.io/api/cookbook/recipe/0001-mvm-image/canvas/p1",
      "type": "Canvas",
      "height": 1800,
      "width": 1200,
      "items": [
        {
          "id": "https://iiif.io/api/cookbook/recipe/0001-mvm-image/page/p1/1",
          "type": "AnnotationPage",
          "items": [
            {
              "id": "https://iiif.io/api/cookbook/recipe/0001-mvm-image/annotation/p0001-image",
              "type": "Annotation",
              "motivation": "painting",
              "body": {
                "id": "http://iiif.io/api/presentation/2.1/example/fixtures/resources/page1-full.png",
                "type": "Image",
                "format": "image/png",
                "height": 1800,
                "width": 1200
              },
              "target": "https://iiif.io/api/cookbook/recipe/0001-mvm-image/canvas/p1"
            }
          ]
        }
      ]
    }
  ]
)

Potential bug location(s):

I'm sure the Extras.allow is the problem:

https://github.com/iiif-prezi/iiif-prezi3/blob/main/iiif_prezi3/skeleton.py#L425-L428

Any other comments:

If this is difficult to handle in the schema and skeleton, maybe we could just make a concerted effort to handle this in helpers and with tests.