Provide context for fields

[karindalziel]

I would like to eventually have a way to easily access context for fields, since we're not namespacing them.

Look to the dpla as an example:

https://api.dp.la/v2/items?q=kittens&api_key=b8f3057f7527a5248ff65e41ff9e9e7f

this isn't urgent for our initial implementation