How to exit app using App itself?

[banool]

In this issue @rparrett helped me find a way to capture a screenshot from a Bevy app and get it from outside the app: #11494.

Problem is, after firing AppExit, the app continues to run. Because I use return_from_run I was hoping there would be some kind of app.quit() function but it doesn't seem to be the case.

Is there a way to exit my App without killing the entire process, either from within the app (in a system) or from outside.

[banool]

What I wanted to do was host an API where when I receive a request, I run an App, take a screenshot, then close the App. Because you can't exit the app without exiting the process this doesn't work. I circumvented this issue by instead running a single App and using a system that waits for messages on a channel, in which it is updates the state based on the API request, and then triggers a screenshot that gets passed back by another channel (this latter part is how the first approach would've worked too).

So I got around it but I still feel AppExit should exit the app, not the process.