added toJson and fromJson functions

lib/model/location.dart

@@ -11,4 +11,15 @@ class Location {
 
   String get address => _address ?? '';
   LatLng get coordinates => _coordinates ?? LatLng.empty();
+
+  factory Location.fromJson(Map<String, dynamic> json) {
+    return Location(
+      address: json['address'] as String,
+      coordinates: LatLng.fromJson(json['coordinates']),
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {'address': address, 'coordinates': coordinates};
+  }
 }