Allow operator shelves to contain grouped apps.

r? @diox @ngokevin 

I have a few tests failing locally, but I'm pretty sure it's an ES misconfiguration and not an actual problem. I'll see what CI thinks.
API endpoint doesn't have to dictate how we structure our index.

I don't think this is good for ES to update the mapping each time we add an app to any group. Can we do this right for shelves and fix it for collections later?