We're changing the default of hide_email_address_taken to true. This is a trade-off we want to make, as it prevents account enumeration with minimal impact on legitimate users. If you forget you have an account and try to sign up again with the same e-mail you'll receive an e-mail letting you know.
The automation plugin has 4 custom field types that are array typed. However, array typed custom fields are deprecated and should be migrated to JSON type.
This commit does a couple of things:
1. Migrate all four custom fields to JSON
2. Fix a couple of small bugs that have been discovered while migrating the custom fields to JSON (see the comments on this commit's PR for details https://github.com/discourse/discourse/pull/26939)
It's currently possible to setup multiple automation rules that trigger each other resulting in an infinite loop. To prevent that, this commit adds a global "circuit breaker" that prevents all automations from triggering while an automation rule is executing.
Internal topic: t/124365.
