Add citation formatter

[josegar74]

This pull request adds the citation formatter to HNAP.

To test, create / load a HNAP metadata and check the formatter:

http://localhost:8080/geonetwork/srv/api/records/UUID/formatters/citation?format=ris

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The pull request is targeted to branch 4.4.x with the label backport-4.2.x to test, when merged, the backport GitHub action to create the pull request for 4.2.x branch.

[jodygarnett]

Needed to make a small change (#421) to test this on a fresh build.

[jodygarnett]

I am getting indexing errors trying to work off 4.4.x HNAP:

Error at xsl:variable on line 1079 column 89 of index.xsl:
  XPST0017: XPath syntax error at char 178 on line 1079 in {...tifier/*[text() != '']/text...}:
    Cannot find a matching 2-argument function named
  {java:org.fao.geonet.util.XslUtil}getTargetAssociatedResourcesAsNode()
2025-02-07T11:34:52,762 ERROR [geonetwork.index] - Indexing stylesheet contains errors: Failed to compile stylesheet. 1 error detected. 
  Marking the metadata as _indexingError=1 in index

See also #421 required to run 4.4.x.

Searching core-geonetwork:

• XslUtil.getTargetAssociatedResourcesAsNode method is not defined on main or 4.2.x branches?

[jodygarnett]

XslUtil.getTargetAssociatedResourcesAsNode() method is not found preventing HNAP records from being indexed.

[jodygarnett]

Rejecting this PR to mark as blocked.
Due to #422 (unrelated issue to indexing records on 4.4.x.)

[josegar74]

@jodygarnett please check #423 fixing the issue #422