datacite: revise relatedIdentifiers in XML metadata

[GraemeWatt]

The relatedIdentifiers in the XML metadata for a whole record currently includes the individual table DOIs:

hepdata/hepdata/modules/records/templates/hepdata_records/formats/datacite/datacite_resource.xml

Line 63 in 50a2498

<relatedIdentifier relatedIdentifierType="DOI" resourceTypeGeneral="Collection" relationType="IsPartOf">{{ overall_submission.doi }}</relatedIdentifier>

This is the same for both unversioned and versioned whole record DOIs. It should be changed so that the unversioned whole record DOI metadata contains the versioned whole record DOIs with relationType="HasVersion". The versioned whole record DOI metadata should contain the unversioned whole record DOIs with relationType="IsVersionOf", and also the individual table and resource file DOIs with relationType="HasPart".

The XML metadata for the individual table and resource file DOIs currently contains only the unversioned whole record DOI with relationType="IsPartOf". This should be changed to the versioned whole record DOI.

It would be necessary to push the revised XML metadata to DataCite after making these changes.

Suggestion from @michamos.