Upgrade to schema43

[t-book]

Overview

https://schema.datacite.org/meta/kernel-4.3/

Changes
Addition of optional “affiliationIdentifier”, “affiliationIdentifierScheme”, and “schemeURI” for affiliation
Addition of optional “schemeURI” for funderIdentifier
Addition of “ROR” to allowed values for funderIdentifierType

Since schema43 affilations can look like

<contributor contributorType="Researcher">
      <contributorName>Huber-Bert, Manfred</contributorName>
      <affiliation affiliationIdentifier="https://ror.org/idkfa3" affiliationIdentifierScheme="ROR" schemeURI="https://ror.org">Something</affiliation>
  </contributor>

Instead of with scheme42

<affiliation>Something</affiliation>

Hence, my feature request is to upgrade the plugin to use schema43

Possible Solutions
From my tests it works to just bump to schema42 and use it in later code lines

ckanext-doi/ckanext/doi/lib/api.py

Line 15 in 59942cf

from datacite import DataCiteMDSClient, schema42