Delete preview channel on close/merge

When a PR is merged or closed, is it possible to detect this and delete the associated preview channel?

I have set the expiry date to 30 days which isn't a problem but when dependabot or renovate decides it's time for 20 PRs then that's a lot of temporary channels being created. There is a limit of 50 preview channels in firebase (I think) and trying to add more fails with a `429`. I set the expiry date to 30 days under the assumption that if I left the PR long enough the channel would expire and it wouldn't be able to redeploy a new one? Correct me if I'm wrong. Firebase also seems to have issues deleting expired channels as they sit there "pending" for a day or so before going.