Investigate why trestle requires seemingly optional values in catalog

[degenaro]

Describe the bug

trestle requires:

• catalog.backmatter.resources.base64.value
• catalog.backmatter.resources.document-ids.identifier
• catalog.backmatter.resources.hashes.value
• catalog.metadata.locations.telephone-numbers.number

To Reproduce

According to outline these seems to be not required.

Environment

• trestle version: 3.9.0

[github-actions]

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