Add JSON metadata export feature

[jazairi]

Why these changes are being introduced:

The metadata team has requested a JSON metadata
export, as it would be easier for them to parse
than the MARC file.

Relevant ticket(s):

• ETD-695

How this addresses that need:

This adds JsonExporter and JsonBatch classes, which serialize thesis metadata and writes the metadata
to a JSON file. This workflow is invoked in the
MarcExportJob, and the output is included
alongside the MARC file in the report email.

It also creates two rake tasks: one to export
the JSON metadata of a single thesis, and one
to export all theses in a given term. This is
primarily for testing purposes.

Side effects of this change:

The export job and batch emails are not clearly
named for the time being. This feels like an
acceptable short-term risk. We plan to retire the
MARC export altogether, at which point we can
rename those files accordingly.

Developer

• All new ENV is documented in README
• All new ENV has been added to Heroku Pipeline, Staging and Prod
• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)
• Stakeholder approval has been confirmed (or is not needed)

Code Reviewer

• The commit message is clear and follows our guidelines
  (not just this pull request message)
• There are appropriate tests covering any new functionality
• The documentation has been updated or is unnecessary
• The changes have been verified
• New dependencies are appropriate or there were no changes

Requires database migrations?

NO

Includes new or updated dependencies?

NO

[coveralls]

coverage: 98.286% (+0.03%) from 98.252% — etd-695 into main

[Copilot]

Pull request overview

Adds a JSON metadata export alongside the existing MARC batch export workflow, so downstream metadata consumers can parse thesis metadata without MARC processing.

Changes:

• Introduces JsonExporter and JsonBatch to serialize thesis metadata and write a JSON export file.
• Updates MarcExportJob and BatchMailer to generate and email both MARC (zip) and JSON attachments.
• Adds rake tasks and tests covering JSON export generation and email attachments.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
app/models/json_exporter.rb	Defines per-thesis JSON-serializable metadata structure.
app/models/json_batch.rb	Builds a batch JSON file wrapping exported theses.
app/jobs/marc_export_job.rb	Generates JSON alongside MARC and attaches both to the batch email.
app/mailers/batch_mailer.rb	Extends batch email to include a JSON attachment and updates subject.
app/views/batch_mailer/marc_batch_email.html.erb	Updates email body to mention JSON alongside MARC.
lib/tasks/metadata.rake	Adds rake tasks for exporting JSON for a single thesis or a term batch.
test/models/json_exporter_test.rb	Adds unit tests for JsonExporter#to_hash.
test/models/json_batch_test.rb	Adds tests for JSON batch file structure/validity.
test/mailers/batch_mailer_test.rb	Updates mailer tests to expect both MARC+JSON attachments and new subject.
test/jobs/marc_export_job_test.rb	Adds coverage for both attachments and JSON validity in the export job email.

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[jazairi]

I'm working with Ben on the content of the JSON file. I think this is ready for code review, but more changes may be coming depending on stakeholder feedback.