add cartonsize api

lib/domain/constants.dart

@@ -5,6 +5,8 @@ const user_collection = "users";
 const invitations_collection = "invitations";
 const privilege_collection = "privileges";
 const markets_collection = "markets";
+const carton_sizes_collection = "carton_sizes";
+
 const packages_collection = "packages";
 const messages_collection = "messages";
 const fcs_shipment_collection = "fcs_shipments";

lib/domain/entities/carton_size.dart

@@ -5,4 +5,26 @@ class CartonSize {
   double width;
   double height;
   CartonSize({this.id, this.name, this.length, this.width, this.height});
+
+
+  Map<String, dynamic> toMap() {
+    return {
+      'id': id,
+      'name': name,
+      'length': length,
+      'width': width,
+      'height': height,
+    };
+  }
+
+  factory CartonSize.fromMap(Map<String, dynamic> map, String id) {
+    return CartonSize(
+      id: id,
+      name: map['name'],
+      length: map['length'],
+      width: map['width'],
+      height: map['height'],
+    );
+  }
+
 }