feat(data_mapping): add constructors for most publictransport classes

lib/transport_helper.dart

@@ -0,0 +1,111 @@
+class Station {
+  final String id;
+  final String name;
+  List<Line>? transportLines;
+  List<Departure>? departures;
+
+  Station({
+    required this.id,
+    required this.name,
+    required this.transportLines
+  });
+
+  factory Station.fromJson(Map<String, dynamic> json) => Station(
+    id: json["id"] as String? ?? json["extId"] as String,
+    name: json["name"],
+    transportLines: json.containsKey("productAtStop")
+        ? json["productAtStop"].map((jsonLine) =>
+            Line.fromJson(jsonLine as Map<String, dynamic>))
+        : const [],
+  );
+}
+
+class Vehicle {
+  final String id;
+  final String name;
+  final List<Departure>? departures;
+
+  Vehicle({
+    required this.id,
+    required this.name,
+    required this.departures
+  });
+
+  factory Vehicle.fromJson(Map<String, dynamic> json)
+}
+
+class Line {
+  final String id;
+  Station? destination;
+  Station? direction;
+  final VehicleType mode;
+  final String name;
+  Color? fgColor;
+  Color? bgColor;
+
+  Line({
+    required this.id,
+    required this.name,
+    required this.mode,
+    this.fgColor,
+    this.bgColor,
+  });
+
+  static const _vehicleTypeAsCatCode = [
+    VehicleType.metro,
+    VehicleType.subway,
+    VehicleType.PLACEHOLDER,
+    VehicleType.bus
+  ];
+
+  factory Line.fromJson(Map<String, dynamic> json) => Line(
+    id: json["lineId"],
+    name: json["name"],
+    mode: _vehicleTypeAsCatCode[int.parse(json["catCode"])],
+    fgColor: Color.fromJson(json["foregroundColor"]) as Color?
+        ?? Color(r: 255, g: 255, b: 255), // fallback
+    bgColor: Color.fromJson(json["backgroundColor"]) as Color?
+        ?? Color(r: 50, g: 50, b: 50), // fallback
+  );
+}
+
+class Departure {
+  String? id;
+  final Vehicle vehicle;
+  final Station station;
+  final DateTime departureTime;
+
+  Departure({
+    required this.vehicle,
+    required this.station,
+    required this.departureTime
+  });
+}
+
+class Color {
+  final int r;
+  final int g;
+  final int b;
+
+  Color({
+    required this.r,
+    required this.g,
+    required this.b
+  });
+
+  factory Color.fromJson(Map<String, dynamic> json) => Color(
+    r: json["r"],
+    g: json["g"],
+    b: json["b"]
+  );
+}
+
+
+enum VehicleType{
+  bus,
+  tram,
+  metro,
+  subway,
+  regionalTrain,
+  PLACEHOLDER
+}