<references> nodes should be turned into @id

[cboettig]

Currently package generates JSON-LD such as:

"creator": {
        "@id": "clarence.lehman",
        "individualName": {
          "givenName": "Clarence",
          "surName": "Lehman"
        }
      },
      "contact": {
        "references": "clarence.lehman"
      }

This should really be turned into:

"creator": {
        "@id": "clarence.lehman",
        "individualName": {
          "givenName": "Clarence",
          "surName": "Lehman"
        }
      },
      "contact": {
        "@id": "clarence.lehman"
      }

Or perhaps more formally:

     "contact": {
        "@id": "clarence.lehman"
       "@type": "@id"
      }

Going in reverse, some care will need to be taken to put the <references> tag back in only when the @type is @id or the @id is the only property.

[cboettig]

This also applies to <describes>, as used in additionalMetadata. Note the mapping here is slightly different: <describes>abc123<describes> becomes: "describes": "abc123", keeping the element name; while references becomes @id. describes needs to be typed as @id so that this functions properly as linked data.

Note that expanding references will also break the strict test of matching numbers of elements, since there's no unique way to collapse back into references, so these will always be embedded.

In contrast, describes should always be collapsed back to the id instead of embedded.