For now - Document the metadata is sent and when
For now - Verify that complete information is being sent for new datasets

Different issue - Resending metadata to PID provider when the schema is modified (Julian to create a new issue)

• related identifier now works for EZID.
• update metadata endpoint throws 404: curl -H "X-Dataverse-key: $API_TOKEN" -X POST http://$SERVER/api/admin/$dataset-id/modifyRegistrationMetadata

@sekmiller and everybody:
Martin Fenner @mfenner (DataCite Technical Director) has pointed this out after the migration from EZID:

something I see a lot in your DataCite metadata is multiple authors in one <creatorName>, e.g. (for DOI 10.7910/dvn/l2ltsc registered yesterday)
<creator>
<creatorName>M. Takayasu, L. Chiesa, J.V. Minervini</creatorName>
</creator>
It should instead be
<creator>
<creatorName>Takayasu, M.</creatorName>
</creator>
<creator>
<creatorName>Chiesa, L.</creatorName>
</creator>
<creator>
<creatorName>Minervini, J.V.</creatorName>
</creator>
Mutliple authors in one <creatorName> not only is not what the schema documentation says, but also makes many things hard or impossible, e.g. adding an ORCD or generating a properly formatted citation in any of the available citation styles.

This does seem like a real issue. Since this (#5060) is related to DOI metadata, and it's already in dev., should we take a look at this problem as well, while we're at it?
Otherwise, let me know and I'll open a new issue.

A quick investigation: I checked a couple of brand-new DOIs that have been minted w/ DataCite since the upgrade yesterday - and they appear to have separate creatorName entries; for example:

<identifier identifierType="DOI">10.7910/DVN/YLUPSB</identifier>  
  <creators> 
    <creator> 
      <creatorName>Dossou-Yovo, Elliott</creatorName>  
      <nameIdentifier schemeURI="https://orcid.org/" nameIdentifierScheme="ORCID">0000-0002-3565-8879</nameIdentifier>  
      <affiliation>(Africa Rice Center)</affiliation> 
    </creator>  
    <creator> 
      <creatorName>Baggie, Idriss</creatorName>  
      <affiliation>(Sierra Leone Agricultural Research Institute)</affiliation> 
    </creator>  
    <creator> 
      <creatorName>Djagba, Justin Fagnombo</creatorName>  
      <affiliation>(Africa Rice Center)</affiliation> 
    </creator>  
    <creator> 
      <creatorName>Swart, Sander</creatorName>  
      <affiliation>(Africa Rice Center)</affiliation> 
    </creator> 
  </creators>  

So my first guess was that this was only a problem with the DOIs migrated from EZID; but then the example Martin provided, above, is ALSO brand-new; minted yesterday.
So this means, I'm guessing, that those 3 authors are actually stored as the single author name in our database (??)
And that would mean this is a problem with our metadata, not with our DOI implementation... OK, either way, this needs to be investigated, whether in the context of this github issue or not.

There was a typo in the doc the curl command for the api is:
curl -H "X-Dataverse-key: $API_TOKEN" -X POST http://$SERVER/api/datasets/$dataset-id/modifyRegistrationMetadata

Regarding @landreev comment: "So this means, I'm guessing, that those 3 authors are actually stored as the single author name in our database (??)", I'm not sure why I never looked into this until now, but Leonid's hunch was right. Many of the datasets in the collection at https://dataverse.harvard.edu/dataverse/MIT-PSFC have multiple authors added in one field. This problem's been documented at #4035, though I suppose the name of the issue should be broadened.