Add author affiliations to DataCite metadata. Ref #2153.

[tompollard]

As discussed in #2153, we do not currently provide author affiliation/s in the metadata that we send to DataCite. This pull request adds affiliations. Example DataCite payloads are shown at: https://support.datacite.org/docs/api-create-dois

e.g.

      "creators": [
        {
          "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"
            }
          ]
        }
      ],

In our case, we will only be providing the affiliation name.