superskunk: take first stab at profile negotiation

Rails cannot process HTTP Accept headers wot have URIs in them due to some very bad regexps and naive string splitting. This commit disables Rails Accept processing and adds actual proper Accept regexps and parsing to the objects controller, plus tests to ensure that this actually works.

All of this should probably be refactored to a different location, and a less-messy solution may be desired. But, at the very least, this gives us a baseline set of tests which any future approach should continue to make pass.

I’m still pretty rusty at Ruby/Rails so advice on better ways of structuring this code is appreciated 😅.

Working towards #964 (closed).