✨(mailbox_manager) add shedule task to fetch domains status

[sdemagny]

Add celery crontab to check and update domains status. This task calls dimail API.

TODO:

• improve task return to give more information
• add notification (here)
• add flower to helm chart

[qbey]

Did you consider adding the sentry for celery? https://docs.sentry.io/platforms/python/integrations/celery/

[Morendil]

When trying this locally, a file src/backend/celerybeat-schedule is created - it would be good to add it to .gitignore ?

[Morendil]

The counting logic is counter-intuitive. A domain is counted as either checked or updated (so you can have 1 updated and 0 checked). What I would expect is that "updated" is a subset of "checked"…

Also, domains that failed verification are not counted at all… and we probably want to report them because the failure logs are going to be hidden in the Celery container's logs, not directly visible here.

I would prefer something like

f"Domains processed: {same_count} not changed, {update_count} updated, {failure_count} failed, {check_count} checked"

with the invariant same_count+update_count+failure_count == check_count.