#Fixes #100: Update to schema43

[t-book]

@alycejenni From my tests this PR covers what is needed to update to the last available schema43 (@ datacite api wrapper). In case I forget something I'm happy about your guidance and working on it.

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 the following 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 schema43 and use it in later code lines as proposed by the PR

https://github.com/NaturalHistoryMuseum/ckanext-doi/blob/59942cf069c2f867459c1396bd9127cb644d7436/ckanext/doi/lib/api.py#L15

[alycejenni]

@t-book you will probably also want to include the changes from #104, making sure you change rightsURI to rightsUri.