About `eframe::App::on_close_event`

In older versions of eframe, there was a `eframe::App::on_close_event` method:

```rust
impl eframe::App for AppUI {

fn on_close_event(&mut self) -> bool {
self.state.on_show_confirm_quit_dialog();
self.state.is_allowed_to_quit()
}

fn on_exit(&mut self, _gl: Option<&eframe::glow::Context>) {
log::info!("on_exit");
}

// ...
}
```
I used it to intercept the user's click on the X button and decide whether to actually exit the app.

However, this method has been removed in newer versions.

Now, how can I achieve my original goal?

The issue names no repository files or tests. Start by checking the current eframe::App API and the lifecycle references for on_exit and the removed on_close_event method; done means documenting or demonstrating the current-version way to show a confirmation dialog and allow or prevent application exit.

Written by the indexing model from the issue text.