Purpose of RouteController unclear

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**Mapbox Navigation SDK version:** 0.39

If I wanted to have turn-by-turn directions textual and visual shown on a map without using the NavigationViewController, rather an instance of NavigationMapView and some labels for the directions, is it still necessary to use a `RouteController`? In the past, I subscribed to various _alerts_ and on that basis triggered a new request and re-route but in the new versions of the API it's unclear to me what's actually required and what isn't. I'm using the `NavigationService` and observe it for `progressDidChange` and `routeControllerDidReroute` notifications and show the routes on the MapView accordingly. In essence, I need to show a route on a map, show an instruction in a label and if the user doesn't follow the current route, re-route and show the new route on the map etc.

Thank you,

Aodh.

Start with the Guides and examples, API reference, and example app linked in the issue, then compare the roles of NavigationService, RouteController, NavigationViewController, and NavigationMapView. Done means documenting which components are required for displaying routes and instructions, observing progress and rerouting, and presenting updated routes without NavigationViewController.

Written by the indexing model from the issue text.