Link directions to routing engine demo #6387
Description
GraphHopper, OSRM, and Valhalla all have their own first-party demo page that exposes more options and details than the Leaflet Routing Machine plugin we’re using, such as via points (A to B to C), turn lanes, elevation profiles, time-sensitive routing, truck routing, and isochrones. Some of these features would be useful to mappers using the OSM website, but others are mainly useful to end users. The end user experience for directions is much more open-ended. We could address their needs by linking out to the selected routing engine’s demo page, adding any supported parameters that can get the page to show something equivalent to the current directions. Then it’s up to the routing engine projects whether they want to facilitate the end user experience to that degree. For example, the GraphHopper and OSRM demo pages both have a convenient button to export GPX (#5224), so there’s less need for us to reimplement that functionality ourselves.