When a dagrun is cleared, recalculate related deadlines if applicable.

[ferruzzi]

bugfix - If the run has a deadline related to the queued_at time, then those should be recalculated when that timestamp is changed.

Manually tested by starting a dag with a deadline and watching the dagrun.queued_at and deadline.deadline_time columns before and after a run cleared via the Airflow UI.

cc @ramitkataria @seanghaeli

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[vincbeck]

Should not we commit the new deadline time?

[ferruzzi]

No, I don't think so. My understanding is that committing or flushing here would break the scheduler session's atomic nature and could result in the database getting a partial update if things went wrong. When I tested manually, this does work as expected. deadline.deadline_time = new_deadline_time is saving that value int he ORM, and the session.flush() on/around L349 writes it all at once.

This pattern also matches how the DagRun updates are handled earlier in the same function (like dr.clear_number += 1 and dr.queued_at = ...).

I'm definitely not an SQL expert, but I'm reasonably confident that this is good how it is.