Give groups a visual border

[tordans]

I want to revisit the idea to add a visual indication for groups.

(…) It lacks the prominent delineation of your example, which I'd like to revisit in the future. From memory we were concerned about introducing too much chrome, considering that objects may be infinitely nested.

Originally posted by @jossmac in #641 (comment)

Current	Proposal

From memory we were concerned about introducing too much chrome, considering that objects may be infinitely nested.

I expect the primary use case to have one group. So IMO the UI should serve this use case first. However, if deeply nested structures are in deed something that happens a lot and the border does indeed make this case noticably worse, we could add custom CSS to only show the border on the first level. Or introduce a new flag like showGrouped: true to opt into the border.

[jossmac]

Thanks for the reminder, @tordans! Keen to take another look at this in the near future

[tordans]

@jossmac happy to help once I get #1285 or "how to get this project running locally" sorted out…