Statusfied

Adds a subscript overload to OrderedDictionary when the Key is an OpenAPI.Respose.StatusCode so that elements can be accessed using the status keyword.

Because OrderedDictionary is both a dictionary and a collection, it has always offered subscript access via both Key and Index (Int). OpenAPI.Response.StatusCode is ExpressibleByIntegerLiteral so accessing ordered dictionaries of OpenAPI.Response from the OpenAPI.Operation responses property by Int is ambiguous:

operation.responses[200] // <- is this `StatusCode` 200 or the 200th index of the collection?

Now, code accessing the dictionary with a status key can be written:

operation.responses[status: 200]

Of course, you can still use any other method of constructing a status code as well:

operation.responses[.status(code: 200)] // <- equivalent to above
operation.responses[.range(.success)]   // <- means the OpenAPI status code string "2XX"
operation.responses[.default]