Allow using event triggers without SUPERUSER

[steve-chavez]

Problem

Currently there's no way to use event triggers. RDS allows it though, see https://web.archive.org/web/20190404104732/https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_PostgreSQL.html#PostgreSQL.Concepts.General.FeatureSupport.EventTriggers. Caveat: the user must delete event triggers when migrating to a new major postgres version.

References:

• https://dba.stackexchange.com/questions/182501/create-event-trigger-as-non-superuser-in-postgres
• https://github.com/orgs/supabase/discussions/9314#discussioncomment-7085076

Solution

Allow event triggers for non superusers.