What this PR does / why we need it:

The underlying goal was to be able to harvest metadata directly from DataCite. Which makes it possible for a Dataverse instance to harvest datasets from institutions and schools who don't maintain their own OAI servers, as long as they register their DOIs with DataCite.

2 major features needed to be added to accommodate this, as described in the linked issue (although one has since been added as a standalone PR #11049 and is already in 6.5). On top of that a few other fixes and improvements have been added. (for example, it is now possible to schedule harvests via the API - this has been a GUI-only feature until now)

Note that everything in this PR is already in prod. use at IQSS via a deployment of a custom experimental patch of v6.5. This had to be done in the context of ongoing collaborations to accommodate the relevant deadlines. The 2 prod. collections involved are:

https://dataverse.harvard.edu/dataverse/bertarelli (note that in this instance the harvested content is included in their subcollections alongside "real", locally-deposited datasets)
https://dataverse.harvard.edu/dataverse/designsafe

Which issue(s) this PR closes:

• Closes Add support for OAI-harvesting from DataCite #10909

Special notes for your reviewer:

I'm about to mark this PR "ready for review". This is true as far as the underlying Dataverse code is concerned however, at the moment the branch is built with a local copy of the customized xoai jars. This is temporary, pending the needed changes being incorporated into a gdcc-released version which is something that needs to happen before this PR is merged.

Suggestions on how to test this:

See the release note and the API guide.

The following is an example harvesting client configuration that will harvest a set made from a single dataset, Gary King's doi:10.7910/DVN/9L6A8X:

{
    "useOaiIdentifiersAsPids": true,
    "useListRecords": true,
    "allowHarvestingMissingCVV": false,
    "set": "~ZG9pOjEwLjc5MTAvRFZOLzlMNkE4WAo=",
    "nickName": "harvest9L6A8X",
    "dataverseAlias": "INSERTYOURCOLLECTION",
    "type": "oai",
    "style": "default",
    "harvestUrl": "https://oai.datacite.org/oai",
    "archiveUrl": "https://oai.datacite.org",
    "archiveDescription": "The metadata for this Dataset was harvested from DataCite. Clicking the dataset link will take you directly to the original archival location, as registered with DataCite.",
    "metadataFormat": "oai_dc"
}

The magic behind the set name in the configuration above, that allows to harvest just this specific dataset:
The native DataCite API query:
https://api.datacite.org/dois?query=doi:10.7910/DVN/9L6A8X
Encoding the query definition in base64:

echo "doi:10.7910/DVN/9L6A8X" | base64
ZG9pOjEwLjc5MTAvRFZOLzlMNkE4WAo=

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

Is there a release notes update needed for this change?:

Additional documentation: