Feedback/success message is never triggered

This used to work in BF 3.x but now the 'Feedback' never gets displayed. The form simply refreshes after a successful submission, no feedback at all.

### **Workaround**:
In `boltforms.form.yml` add the `redirect` property under `feedback`, like so:
```
feedback:
success: Message sent! #<--- this is not working
redirect:
target: page/contact?success=true
```

In my case `page/contact` is the record that loads my contact form, so in its template I use the following code:
```
{% if app.request.get('success') == true %}

Message sent!

{% else %}
{{ boltforms('contact') }}
{% endif %}
```

That way the success message is only displayed when triggered by the success redirect.