✨ Internal train network structure

- Defines Network, StopArea, StopPoints and JourneySections
- Loads them from json using the build_from_json method

lib/trenesis/network/graph.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#include <nlohmann/json.hpp>
+#include "trenesis/geojson.h"
+
+namespace trenesis {
+	using json = nlohmann::json;
+
+	struct StopPoint;
+
+	struct StopArea {
+		std::string id;
+		std::string label;
+		std::string name;
+		Point coord;
+
+		std::unordered_map<std::string, std::unique_ptr<StopPoint>> stop_points;
+
+		StopArea(std::string id, std::string label, std::string name, Point coord);
+	};
+
+	struct JourneySection {
+		StopPoint* origin;
+		StopPoint* destination;
+		// TODO: use real types for times
+		std::string departure_time;
+		std::string arrival_time;
+	};
+
+	struct StopPoint {
+		std::string id;
+		std::string label;
+		std::string name;
+		Point coord;
+		StopArea* stop_area;
+
+		std::vector<JourneySection> departures;
+
+		StopPoint(
+				std::string id,
+				std::string label,
+				std::string name,
+				Point coord,
+				StopArea* stop_area
+				);
+	};
+
+	struct Network {
+		std::unordered_map<std::string, std::unique_ptr<StopArea>> stop_areas;
+
+		static Network build_from_json(const json& vehicle_journeys, const json& stop_points);
+	};
+
+}