I have a web application that provides APIs to be invoked. In my use case, I would like to invoke certain APIs when opening and closing a code review. However I discovered that Herald Rules does not support custom actions. It would be nice if the task could be running some PHP or shell script.

I hope Herald Rules is the right place for this type of use case to go as I was trying to make a plug in for Phabricator but realized that there is no way to listen to this type of updates.