Improve metadata mapping for example datasets

[cc-a]

• Issue: #44

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This is a revisit of the issue that improves the mapping between the source datacite schema and the invenio rdm schema by:

• Adding license metadata (rights)
• Date metadata
• Previously some datacite related identifiers were being mapped into the references section of the invenio schema. Update here so that these are now related identifiers under the invenio schema as well.

Developer Checklist

Developers should review and confirm each of these items before requesting review

• [ ] Code meets acceptance criteria from issue
• [ ] Unit tests are written and all pass
• [ ] User Test Scripts (if required) are written and have been run through
• [ ] Code documentation and related non-code documentation has all been updated

Reviewer Checklist

Reviewers should review and confirm each of these items before approval If there are multiple reviewers, this section can be duplicated for each reviewer

• [ ] Code meets acceptance criteria from issue
• [ ] Unit tests are written and all pass
• [ ] User Test Scripts (if required) are written and have been run through
• [ ] Code documentation and related non-code documentation has all been updated
• [ ] Migation has been created and tested

Testing

List user test scripts that need to be run

List any non-unit test scripts that need to be run