Fixes #2619 News export API empty value handling

[tadean]

Description

For some of the API fields, az_quickstart/export/az_news/v1/az_news.json represents empty values as [ ], when the value of the equivalent non-empty field is normally a json object containing the field properties (this includes fields like field_az_media_thumbnail_image, field_az_enterprise_attributes and field_az_media_image.)

This PR changes handling of those fields to produce null rather than [ ] when those fields are empty. This is to increase data type consistency of the API.

Discussion for review: is null or an empty object (rather than an array) preferable?

update: the PR has been updated to instead provide an empty object { } , rather than null.

Related issues

Closes #2619

How to test

• enable az_news_export az_enterprise_attributes_import
• Create news data
• Verify some data has images and others do not
• Verify that some data has enterprise attributes and others do not
• Visit az_quickstart/export/az_news/v1/az_news.json and verify that empty field values produce null rather than [ ]

Types of changes

Arizona Quickstart (install profile, custom modules, custom theme)

• Patch release changes
  • Bug fix
  • Accessibility, performance, or security improvement
  • Critical institutional link or brand change
  • Adding experimental module
  • Update experimental module
• Minor release changes
  • New feature
  • Breaking or visual change to existing behavior
  • Upgrade experimental module to stable
  • Enable existing module by default or database update
  • Non-critical brand change
  • New internal API or API improvement with backwards compatibility
  • Risky or disruptive cleanup to comply with coding standards
  • High-risk or disruptive change (requires upgrade path, risks regression, etc.)
• Other or unknown
  • Other or unknown

Drupal core

• Patch release changes
  • Security update
  • Patch level release (non-security bug-fix release)
  • Patch removal that's no longer necessary
• Minor release changes
  • Major or minor level update
• Other or unknown
  • Other or unknown

Drupal contrib projects

• Patch release changes
  • Security update
  • Patch or minor level update
  • Add new module
  • Patch removal that's no longer necessary
• Minor release changes
  • Major level update
• Other or unknown
  • Other or unknown

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[tadean]

Updated with an alternate experimental approach that adds a Normalizer service that ensures that properties the schema defines as json objects will still be serialized as objects when empty.

[tadean]

Kim Rosema on the Trellis team reported that the current approach in this PR of providing an empty object seems to resolve the issue with the integration on their end.