Template versioning tracks breaking changes

Jobs that reference a template by mutable name always resolve to the current version. When a template is updated mid-campaign, queued jobs that have not yet been processed will render the new version instead of the version that was live when the campaign was dispatched. Recipients in the same send batch receive different content depending on when their job was processed. ISO-25010:2011 maintainability.modifiability requires that changes to one component do not silently alter the behavior of unrelated queued work.

Pin a templateVersion identifier on every job at enqueue time so the worker loads the exact version that was current when the campaign was dispatched:

await emailQueue.add('send', {
  to: recipient.email,
  templateId: 'welcome',
  templateVersion: 'v2.1.0', // Pinned at dispatch time
  mergeFields: { firstName: recipient.firstName }
})

In the worker, query db.emailTemplate.findFirstOrThrow({ where: { slug: templateId, version: templateVersion } }) so a template update never silently alters in-flight jobs.