What issues does your PR fix?

Currently, the db-migrations Deployment will hang forever after printing WARNING - there are unapplied db migrations, triggering apply... when attempting to upgrade airflow from 2.2.X to something newer.

When this happens, the only solution is to restart the PgBouncer Pod.

What does your PR do?

As of Airflow 2.2.0, the upgradedb() command now creates a PG_ADVISORY_LOCK.

We run PgBouncer in pool_mode = transaction, in this mode, locks will never be released, because the "lock" and "unlock" statements are necessarily in separate transactions, and there is no guarantee that these transactions will be run on the same session by PgBouncer.

To solve this, this PR uses the server_reset_query and server_reset_query_always configs of PgBouncer, to run a SELECT pg_advisory_unlock_all() query after each transaction. This ensures any locks that were created are immediately removed. In our case, this is fine, because only one instance of db-migrations will run at a time (in most situations), so the locks arent strictly nesseesary.

Checklist

For all Pull Requests

• Commits are signed off
• Commits have semantic messages
• Documentation updated
• Passes ct linting

For releasing ONLY

• Chart.yaml version bumped
• CHANGELOG.md updated