Allow users to specify a class for each way

This adds the ability to mark ways with a user-defined
class in the profile. This class information will be included
in the response as property of the RouteStep object.

src/engine/api/json_factory.cpp

@@ -265,6 +265,18 @@ util::json::Object makeRouteStep(guidance::RouteStep step, util::json::Value geo
     route_step.values["maneuver"] = makeStepManeuver(std::move(step.maneuver));
     route_step.values["geometry"] = std::move(geometry);
 
+    if (!step.classes.empty())
+    {
+        util::json::Array classes;
+        classes.values.reserve(step.classes.size());
+        std::transform(
+            step.classes.begin(),
+            step.classes.end(),
+            std::back_inserter(classes.values),
+            [](const std::string &class_name) { return util::json::String{class_name}; });
+        route_step.values["classes"] = std::move(classes);
+    }
+
     util::json::Array intersections;
     intersections.values.reserve(step.intersections.size());
     std::transform(step.intersections.begin(),

src/engine/guidance/post_processing.cpp

@@ -486,6 +486,7 @@ void trimShortSegments(std::vector<RouteStep> &steps, LegGeometry &geometry)
         auto &new_next_to_last = *(steps.end() - 2);
         next_to_last_step.AdaptStepSignage(new_next_to_last);
         next_to_last_step.mode = new_next_to_last.mode;
+        next_to_last_step.classes = new_next_to_last.classes;
         // the geometry indices of the last step are already correct;
     }
     else if (util::coordinate_calculation::haversineDistance(