Delete stopped review apps

Problem to solve

One reason that pushing to www-gitlab-com is slow is because the repository advertised nearly 300k refs (7MB uncompressed). This means pushing 5kb of new data requires downloading 7MB first. This adds 5-10 seconds to every push.

Further details

Approx 200k of those refs (70%) are from stopped environments.

Proposal

Write a script to search for environments that are stopped and over 1 month old, and delete them.

Also, ensure that we attempt to delete the associated subdirectory from the GCP bucket at the same time.