feat: notify diego of route updates

After updating a route via the new update route endpoint, it was only
stored in the database. Since routes can be changed without restarting
the application this commit adds logic to also push the update to diego.

Resolves: #4286

Author: maxmoehl

app/actions/route_update.rb

@@ -6,6 +6,10 @@ def update(route:, message:)
 
         route.save
         MetadataUpdate.update(route, message)
+
+        route.route_mappings.each do |route_mapping|
+          ProcessRouteHandler.new(route_mapping.process).notify_backend_of_route_update
+        end
       end
 
       route