Provide `onRoutesRequestFailure` reason information

[Guardiola31337]

Currently, we're reporting back a Throwable with a tweaked message as a result of

mapbox-navigation-android/libnavigation-core/src/main/java/com/mapbox/navigation/core/MapboxNavigation.kt

Lines 386 to 389 in 306f291

	fun requestRoutes(
	routeOptions: RouteOptions,
	routesRequestCallback: RoutesRequestCallback
	): Long {

mapbox-navigation-android/libnavigation-core/src/main/java/com/mapbox/navigation/core/directions/session/RoutesRequestCallback.kt

Line 34 in 306f291

fun onRoutesRequestFailure(throwable: Throwable, routeOptions: RouteOptions)

Clients can parse the string Throwable.message or print the whole thing but there isn't an easy way to tell the user the reason e.g. if it was offline or service error:

if ( /* is offline error */ ) 
   // display prompt telling user to check network connection
else
   // display user message apologizing for service being down

This can't be easily implemented with given information from the Throwable.

This ticket tracks the feature request of adding some kind of Error object including the Reason so that developers can use this extra information to act accordingly to their use cases (e.g. to determine what messaging to display).

Reasons may include offline vs service error, authentication failure, bad request, etc.

cc @mapbox/navigation-android

[Guardiola31337]

Capturing more feedback on the topic.

Also depending on how the service handles it, other possible error reasons could be:

• if maximum route length (if there is one?) for a walking or driving route is exceeded
• if the start and end points of the route are the same (with no waypoints in-between)
  basically any problems with the route that we should message the client about

[Guardiola31337]

cc @mapbox/navigation-ios

[1ec5]

In Swift, this code associates Directions API error codes with enumeration values that are included in the callback for route requests.