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.
This commit adds a new option to the `user_updated` trigger of the automation plugin to only trigger an automation for new users that join after the automation is enabled.
Internal topic: t/125829/9.