feat: datatracker event notification via celery

[jennifer-richards]

This adds celery infrastructure and a framework for notifying datatracker of events. Attempts redelivery with exponential(ish) backoff out to once every 15 minutes with a suggestion of letting it retry delivery for a week at that terminal rate. After retries are exhausted, reports failure to admins via email that can be reviewed in mailpit for dev/staging.

This requires the datatracker API in ietf-tools/datatracker#9975. So far it only uses the metadata / Document-creation API. It does not yet upload contents but has a stub in place for that. This also does not connect the publication task to events or the UI. For now, it can be manually run from the shell.

Example using a random RfcToBe:

In an app shell:

>>> from datatracker.tasks import *
>>> notify_rfc_published_task.delay(rfctobe_id=RfcToBe.objects.last().pk)
<AsyncResult: ba375382-32f4-4794-b7db-763356aa76be>```

In the celery log:

celery-1  | [2025-08-13 20:40:39.591] (INFO) Task datatracker.tasks.notify_rfc_published_task[73b82d17-0c61-4ed8-9832-a9675f188aa0] received (celery.worker.strategy)
celery-1  | [2025-08-13 20:40:39.646] (INFO) Task datatracker.tasks.notify_rfc_published_task[73b82d17-0c61-4ed8-9832-a9675f188aa0] succeeded in 0.05237758300791029s: None (celery.app.trace)

If I turn set the max_retries to 2 and raise a RuntimeError in the task, this shows up in the celery log

[2025-11-21 19:45:25.119] (INFO) Task datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] received (celery.worker.strategy)

[2025-11-21 19:45:25.233] (INFO) Task datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] received (celery.worker.strategy)

[2025-11-21 19:45:25.236] (INFO) Task datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] retry: Retry in 3s: RuntimeError() (celery.app.trace)

[2025-11-21 19:45:28.228] (ERROR) Task datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] log: Emailing admins to report failure: datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] with args=[1] and kwargs={}. Giving up after 1 retries.

[2025-11-21 19:45:28.239] (ERROR) Task datatracker.tasks.notify_rfc_published_task[4a649274-aaa6-4ac0-8258-7df26c0b2a9a] raised unexpected: RuntimeError() (celery.app.trace)

and an email is sent to ADMINS with the task name/ID/args/kwargs and a traceback if an exception occurred.

This does not yet add k8s infrastructure for celery.

[rjsparks]

Would expect this to be None, which means no became_rfc relationship gets created

[jennifer-richards]

ok - I've adjusted this to handle rfctobe.draft is None. Purple overall will need some adjustment to deal with that I think (immediately adjacent issue is that purple doesn't actually know the title except through the draft). The updated code here should just work when we straighten that out, though.