Check for hasPart path from root data entity to data entities

[floWetzels]

The RO-Crate specification requires every data entity to be directly or indirectly linked from the root data entity via the attribute hasPart. However, the current validator only checks for a direkt link from another Dataset object. Here the respective SHACL code:

sh:path [ sh:inversePath schema_org:hasPart ] ;
sh:node schema_org:Dataset ;
sh:minCount 1 ;

After discussing this with @elichad, we concluded that this is a bug and should be fixed. If there are isolated Dataset objects with cyclic references, the validator deems this a valid RO-Crate. A simple example crate that triggers this behavior is attached at the bottom.
A fix for this issue using sh:oneOrMorePath, sh:qualifiedValueShape and sh:qualifiedMinCount, as well as corresponding test cases, are implemented on this branch: https://github.com/nfdi4plants/rocrate-validator/tree/fix-cyclic-datasets.
If we didn't overlook something that makes the current behavior correct or intended, I could open a PR.

Example crate:

{
    "@context": [
        "https://w3id.org/ro/crate/1.1/context"
    ],
    "@graph": [
        {
            "@id": "ro-crate-metadata.json",
            "@type": "CreativeWork",
            "conformsTo": {
                "@id": "https://w3id.org/ro/crate/1.1"
            },
            "about": {
                "@id": "./"
            }
        },
        {
            "@id": "./",
            "@type": "Dataset",
            "name": "Root",
            "description": "Root Dataset",
            "datePublished": "2024-05-17T01:04:52+01:00",
            "hasPart": [
            ],
            "license": "CC-BY-4.0"
        },
        {
            "@id": "dataset1/file1.txt",
            "@type": "File",
            "description": "A file",
            "encodingFormat": "text/plain",
            "name": "file1.txt"
        },
        {
            "@id": "dataset2/file2.txt",
            "@type": "File",
            "description": "Another file",
            "encodingFormat": "text/plain",
            "name": "file2.txt"
        },
        {
            "@id": "dataset1/",
            "@type": "Dataset",
            "name": "Dataset 1",
            "description": "First dataset",
            "hasPart": [
                {
                    "@id": "dataset1/file1.txt"
                },
                {
                    "@id": "dataset2/"
                }
            ]
        },
        {
            "@id": "dataset2/",
            "@type": "Dataset",
            "name": "Dataset 2",
            "description": "Second dataset",
            "hasPart": [
                {
                    "@id": "dataset2/file2.txt"
                },
                {
                    "@id": "dataset1/"
                }
            ]
        }
    ]
}