Investigate whether format verification is working

[tmorrell]

Package version (if known): v1.1.2

Describe the bug

The date format verification https://github.com/inveniosoftware/datacite/blob/b15db91e1231135e5f2dba0cadca0c72ede037cf/datacite/schemas/datacite-v4.3.json#L80 may not be used by default https://python-jsonschema.readthedocs.io/en/latest/validate/#validating-formats or be implemented correctly.