feat: add "string" type for metadata fields

[vera]

What this PR does / why we need it:

See #11147

Which issue(s) this PR closes:

• Closes Feature Request: Add "string" type for metadata fields #11147

Special notes for your reviewer:

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Suggestions on how to test this:

1. Load a metadata block TSV that defines a field with type "string"

   example: https://gist.github.com/vera/fc39e7b0bb0e9da7dc24a41c680f6d59

   curl http://localhost:8080/api/admin/datasetfield/load -H "Content-type: text/tab-separated-values" -X POST --upload-file stringtest.tsv

2. Activate metadata block

   curl curl -H "X-Dataverse-key:$API_TOKEN" -X POST -H "Content-type:application/json" -d "[\"citation\", \"stringTest\"]" http://localhost:8080/api/dataverses/:root/metadatablocks

3. Update Solr schema

   curl "http://localhost:8080/api/admin/index/solr/schema" | ./update-fields.sh schema.xml

   docker cp schema.xml solr-1:/var/solr/data/collection1/conf/schema.xml

   curl "http://localhost:8983/solr/admin/cores?action=RELOAD&core=collection1"

4. Confirm that the updated Solr schema contains a new field with type "string"

    <field name="testStringField" type="string" multiValued="false" stored="true" indexed="true"/>
   ...
    <copyField source="testStringField" dest="_text_" maxChars="3000"/>
   

5. Create a new dataset via the UI (or API)

   

6. Verify the string value correctly ends up in Solr and can be seen on the dataset page

   

   

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

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Is there a release notes update needed for this change?:

Yes, I think that would be good. I've added a release note as part of this PR.

Additional documentation:

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