Make it possible to return HTTP 406 when there's no match

[p-himik]

reitit.coercion.malli/create uses :content-types of a resource to determine which response content types are supported.

Muuntaja completely ignores that key and seemingly doesn't allow its users to configure a strict set of response content types.

E.g. I want for my API to only produce application/edn or application/transit+json. But even if I set :default-format in Muuntaja config to application/edn and restrict :formats to application/edn, a client will get EDN instead of HTTP 406 even when it specifies that it can't handle anything but e.g. application/json by using the Accept header.

An additional point worth considering is that different API endpoints might have different available content types.