Make individual inlines in the inlines list collapsible

[fng3r]

Is it a third party application feature request?

No

Describe your feature request

Now you have capability to collapse all related models by settings classes = ["collapse"] in the inline class. But there is no way to make individual inlines collapsible.

This is how it looks being uncollapsed

This is what requested

Scenario when it would be useful is pretty simple. When you have a couple of dozens of items it would be much easier to detect needed ones if the list was compact, especially in cases when inlines itself have massive forms and you need to scroll several screens to find the one you want

[lukasvinclav]

Implemented here: #1373