Fix/bulk send file attachments missing

[whabanks]

Summary | Résumé

This PR fixes an issue where file attachment metadata was not persisted to notification.personalisation for notifications belonging to a job.

When performing a one-off send, admin attaches file metadata to the notification's personalisation before calling API. This change ensures that the same occurs for notifications sent during a bulk job. Because the job CSV only contained user provided columns, we weren't writing the template attachment metadata into each notification's personalisation, resulting in the notification history page failing to display attachment metadata for notifications belonging to a job.

• Added _persist_template_attachment_metadata to send_to_providers.py. send_email_to_provider calls to update the personalisation dict prior to persisting the status -> sending update to the db. This method will only add to metadata if it does not yet exist and thus should not affect the one-off sending flow.
• Added file_size to the Redis cache key for job attachments.

Related Issues | Cartes liées

• https://docs.google.com/document/d/1m_EzXNJbqjJH-WLzxRKMtO4k5CAHwk51uCXi7xJQR44/edit?tab=t.0#task=EWrnCLBdziEITHb7

Test instructions | Instructions pour tester la modification

1. Hook your local up to staging (Admin + API) and run document download locally
2. Send a bulk job

• Confirm you received the file attachments in the emails you received

3. From the dashboard navigate to one of the notifications belonging to the job

• Note that the file attachments & size are listed below the content block

Release Instructions | Instructions pour le déploiement

None.

Reviewer checklist | Liste de vérification du réviseur

• This PR does not break existing functionality.
• This PR does not violate GCNotify's privacy policies.
• This PR does not raise new security concerns. Refer to our GC Notify Risk Register document on our Google drive.
• This PR does not significantly alter performance.
• Additional required documentation resulting of these changes is covered (such as the README, setup instructions, a related ADR or the technical documentation).

⚠ If boxes cannot be checked off before merging the PR, they should be moved to the "Release Instructions" section with appropriate steps required to verify before release. For example, changes to celery code may require tests on staging to verify that performance has not been affected.

[Copilot]

Pull request overview

Fixes bulk-job email notifications missing template attachment metadata in notification.personalisation, which breaks attachment display on the notification history page.

Changes:

• Adds file_size to cached/DB template-file metadata used during bulk sends.
• Introduces _persist_template_attachment_metadata and calls it from send_email_to_provider to populate _file_N personalisation entries for bulk notifications.
• Adds tests covering persistence behavior and integration with send_email_to_provider.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
app/delivery/send_to_providers.py	Adds file_size to template file metadata, introduces metadata persistence helper, and calls it during email send flow.
app/celery/tasks.py	Includes file_size when pre-caching template file metadata for jobs.
tests/app/delivery/test_template_attachments.py	Adds unit + integration tests for persisting template attachment metadata into notification personalisation.

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[andrewleith]

LGTM - I can see the attachment list on a bulk notification history page now!