oai_dc export: use publication date if production date is not set

[tcoupin]

What this PR does / why we need it:

Production date is used as date tag when export dataset to oai_dc.
This PR use the publication date if production is not set.

Which issue(s) this PR closes:

Related to #8103 and #8732

Special notes for your reviewer:

Suggestions on how to test this:

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:

[scolapasta]

Hi @tcoupin, for this next sprint we are catching up on Community PRs. Would you mind updating/ refreshing thiis PR from develop? Thanks!

[tcoupin]

I rebase on develop branch

[coveralls]

Coverage decreased (-0.0005%) to 19.88% when pulling 97cf6bc on tcoupin:oaidc-date into 9686ab8 on IQSS:develop.

[sekmiller]

Looks good. thanks for the contribution and rebasing.

[pdurbin]

Looks good! Merged! Thanks @sekmiller @jggautier and @landreev for the discussion.

At release time, @jggautier plans to update our crosswalk doc to explain the new date handling. I linked to the doc in the release note snippet I added: 97cf6bc

We also discussed a bit how the oai_dc format is not available in the dropdown as an export. However you can hack the URL to get to it: https://dataverse.harvard.edu/api/datasets/export?exporter=oai_dc&persistentId=doi%3A10.7910/DVN/TJCLKP . If we ever want to change this, it's just a matter of flipping the isAvailableToUsers boolean in DublinCoreExporter:

https://github.com/IQSS/dataverse/blob/v5.12/src/main/java/edu/harvard/iq/dataverse/export/DublinCoreExporter.java#L52-L54

Anyway, thanks, @tcoupin! Please keep the pull requests coming! 🎉