In OpenAIRE/oai_datacite export, when user doesn't choose a relationType, use "IsSupplementTo"

Overview of the Feature Request

When the user adds a Related Publication but does not choose an option from the Related Publication Relation Type dropdown, the OpenAIRE/oai_datacite export should use "IsSupplementTo" as the default relationType, as the DataCite/Datacite export already does. Currently, the OpenAIRE/oai_datacite export uses "IsCitedBy" as the default instead.

This issue is part of a larger effort to align both metadata exports, described in https://github.com/IQSS/dataverse/issues/11916 and https://github.com/IQSS/dataverse/issues/12281.

What kind of user is the feature intended for?

API User, Superuser, and Sysadmin

What inspired the request?

This is part of a larger effort to align the OpenAIRE/oai_datacite and DataCite/Datacite metadata exports. There is more context at https://github.com/IQSS/dataverse/issues/11916 and https://github.com/IQSS/dataverse/issues/12281.

What existing behavior do you want changed?

Currently, when the user adds a Related Publication but does not choose an option from the Related Publication Relation Type dropdown, the DataCite/Datacite export uses "IsSupplementTo" as the default relationType. For example:

<relatedIdentifier
    relationType="IsSupplementTo"
    relatedIdentifierType="ARK">12345
</relatedIdentifier>

The OpenAIRE/oai_datacite export uses "IsCitedBy" as the default instead. For example:

<relatedIdentifier
    relationType="IsCitedBy"
    relatedIdentifierType="ARK">12345
</relatedIdentifier>

The OpenAIRE/oai_datacite export should be changed to use "IsSupplementTo" as the default relationType when the user doesn't choose an option from the Related Publication Relation Type dropdown, matching the behavior of the DataCite/Datacite export.

Any open or closed issues related to this feature request?

• https://github.com/IQSS/dataverse/issues/11916
• https://github.com/IQSS/dataverse/issues/12281

Compare the OpenAIRE/oai_datacite and DataCite/Datacite export implementations, focusing on how a missing Related Publication relation type becomes the XML relationType value. Confirm the OpenAIRE export currently produces IsCitedBy and should match the DataCite export's IsSupplementTo behavior. Verify the generated relatedIdentifier XML for an omitted relation type.