Extended interactive app descriptions

[robinkar]

We would like to have the possibility of providing longer descriptions and help text for the apps that would be visible only inside the app forms.
The problem with adding it to the description in manifest.yml is that it shows up in the tooltips for the apps:

Instead, we would like to separate tooltip and the longer description to have something like this:

[johrstrom]

OK - the only question really is what's the manifest key. header? form_header?

[robinkar]

form_header seems quite good.
Alternatives could be something like extended_description and long_description, but I think form_header might be better than those.