DB migrations fail with postgres >=18 #1678
Description
Specifically: Migration 15-fix-event-constraints.sql cannot be applied, causing all subsequent migrations to be skipped.
So we cannot fix this with a new migration, but changing old migrations is also problematic because that would break existing deployments that are upgrading. A possible fix for those cases (if we were to fix it in migration 15) would be to run db unsafe-overwrite-migrations, but that is usually only for dev purposes and would complicate updates.
We should investigate other possibilites.
Some technical details:
PG 18 starts exposing NOT NULL constraints as proper pg_constraints that now show up in information_schema views, which we use in migration 15. That makes the constraint lookup return extra rows and fail. The info is a bit hidden in the release notes.