Add author affiliations to DataCite metadata

[Tom Pollard]

Minor thing, but I'd like to improve the quality of the metadata that we send to DataCite when registering DOIs. Some examples of "rich metadata" are provided at: https://support.datacite.org/docs/api-create-dois

We do not currently provide the author affiliations/s, so these could be added:

        {
          "name": "Miller, Elizabeth",
          "nameType": "Personal",
          "givenName": "Elizabeth",
          "familyName": "Miller",
          "affiliation": [
            {
              "affiliationIdentifier": "https://ror.org/04wxnsj81",
              "affiliationIdentifierScheme": "ROR",
              "name": "DataCite",
              "schemeUri": "https://ror.org/"
            },
            {
              "affiliationIdentifier": "https://ror.org/05dxps055",
              "affiliationIdentifierScheme": "ROR",
              "name": "California Institute of Technology",
              "schemeUri": "https://ror.org/"
            }
          ],
          "nameIdentifiers": [
            {
              "schemeUri": "https://orcid.org",
              "nameIdentifier": "https://orcid.org/0000-0001-5000-0007",
              "nameIdentifierScheme": "ORCID"
            }
          ]
        }

To begin, we can provide a plain string. Later, we might want to try to incorporate Affiliation Identifiers too, e.g. RORs ("a global, community-led registry of open persistent identifiers for research organizations": https://ror.org/)

[bemoody]

Should be fixed by pull #2154.