Subclasses of DirectionsOptions cannot override urlQueryItems

[1ec5]

#343 added an overridable DirectionsOptions.urlQueryItems property for the purpose of enabling applications to take advantage of not-yet-ready-for-primetime Directions API parameters. Unfortunately, 593efd3 for #382 made the property internal. It was probably an oversight, and I think we can safely reexpose the property. MatchOptions is unaffected; its urlQueryItems property remains open.

Until we reexpose DirectionsOptions.urlQueryItems publicly, the workaround would be to take the result of Directions.url(forCalculating:) or similar, use URLComponents to parse the URL and add more urlQueryItems, get the URL back out, request that URL using URLSession, and use JSONDecoder to decode the response as a RouteResponse – basically, everything that Directions.calculate(_:completionHandler:) normally does for you.

/cc @mapbox/navigation-ios

[1ec5]

Some of the unit tests supposedly exercise this functionality from an application point of view, but they have access to the property anyways because MapboxDirections is imported as @testable, giving the test bundle access to even fileprivate and internal symbols.