In DataCite/Datacite export, when user chooses cstr and URL from Related Publication Identifier Type dropdown, add cstr and URL to related identifiers

[jggautier]

Overview of the Feature Request

When the user adds a Related Publication and chooses cstr or URL from the Related Publication Identifier Type dropdown, the DataCite/Datacite export should include the related identifiers, as the OpenAIRE/oai_datacite export already does. Currently, the DataCite/Datacite export does not include the related identifiers in these cases.

This issue is part of a larger effort to align both metadata exports, described in #11916.

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 in the closed issue at #11916.

What existing behavior do you want changed?

Currently, when the user chooses cstr or URL from the Related Publication Identifier Type dropdown, the DataCite/Datacite export does not include the related identifier. See #11089 for more context.

The OpenAIRE/oai_datacite export does include the related identifier in these cases. For example:

<relatedIdentifier
    relationType="IsCitedBy"
    relatedIdentifierType="cstr">CSTR:16666.11.nbsdc.J0V2mNIU
</relatedIdentifier>
<relatedIdentifier
    relationType="IsCitedBy"
    relatedIdentifierType="URL">https://url.org
</relatedIdentifier>

The DataCite/Datacite export should be changed to include related identifiers when the user chooses cstr or URL as the identifier type, matching the behavior of the OpenAIRE/oai_datacite export.

Any open or closed issues related to this feature request?

#11916
#11089