Json schema tweaks

[codycooperross]

Purpose

• Removes validation for identifier, which isn't present in the database schema.
• Validates identifiers instead of alternate_identifiers to align with database column naming and internal identifiers attribute naming.
• Validates types instead of raw_types and allows additional properties (like bibtex and schemaOrg) in the JSON Schema.
• Removes requirement for types.resourceType, which is an optional field.
• Removes update_field_of_science, which seemed to cull some subject properties; for example, when subjects.subject is submitted as an integer.
  • We intended to remove this method as part of current work here anyway: https://github.com/datacite/product-backlog/issues/465
• Allows empty string affiliation.name since this is permitted by the XSD.
• Allows nil for identifiers.identifier and identifiers.identifierType since nils can be appear for these properties when reading XML.
• Does not require titles.title or subjects.subject since these can be blank if the elements are submitted empty via XML.

closes: Add github issue that originated this PR

Approach

Open Questions and Pre-Merge TODOs

Learning

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• New feature (non-breaking change which adds functionality)

• Breaking change (fix or feature that would cause existing functionality to change)

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