publicationYear type in JSON output is `int` whenever schema says it to be a regex matching string

[yarikoptic]

Discovered in the course of the exploration of the "datacite metadata schema life-cycle" in

• No "identifier" to correspond to the one in datacite XSD/docs? inveniosoftware/datacite#102 (comment)

ATM datacite fabric returns records with publicationYear as int, although original schema in XSD (https://github.com/datacite/schema/blob/e39faa8ee9b28ac4b5806b5b77daa1a1d0c304f4/source/meta/kernel-4/metadata.xsd#L679) states it to be "YearType" to be a string, or in Documentation (https://datacite-metadata-schema.readthedocs.io/en/4.5/properties/publicationyear/#publicationyear) does not state it to be numeric; and even JSON examples (e.g. https://github.com/datacite/schema/blob/e39faa8ee9b28ac4b5806b5b77daa1a1d0c304f4/source/json/kernel-4.3/example/datacite-example-video-v4.json#L46) have it as string.

Even if I see more sense for it to be a numeric, with a reasonable range defined for validation, I think returned value should conform to the original schema and thus be a string across different serializations.

Or, alternatively -- is there a JSON model of "datacite output records" (as opposed to input)?