feat: 972 - new "product_type" field for Product (openfoodfacts#973)

New file:
* `product_type.dart`: Type used at the product level (e.g. "this is a pet food product").

Impacted files:
* `openfoodfacts.dart`: exported new file `product_type.dart`
* `product.dart`: added a new `ProductType?` field
* `product.g.dart`: (generated)

lib/openfoodfacts.dart

@@ -48,6 +48,7 @@ export 'src/model/parameter/without_additives.dart';
 export 'src/model/per_size.dart';
 export 'src/model/product.dart';
 export 'src/model/product_freshness.dart';
+export 'src/model/product_type.dart';
 export 'src/model/product_image.dart';
 export 'src/model/product_packaging.dart';
 export 'src/model/product_result_field_answer.dart';

lib/src/model/product.dart

@@ -13,6 +13,7 @@ import 'nutriments.dart';
 import 'owner_field.dart';
 import 'product_image.dart';
 import 'product_packaging.dart';
+import 'product_type.dart';
 import '../interface/json_object.dart';
 import '../utils/json_helper.dart';
 import '../utils/language_helper.dart';
@@ -90,6 +91,10 @@ class Product extends JsonObject {
   @JsonKey(name: 'code')
   String? barcode;
 
+  /// Type of the product (e.g. "pet food").
+  @JsonKey(name: 'product_type')
+  ProductType? productType;
+
   /// Product name, either set directly or taken from one of the localizations.
   ///
   /// Rather use [productNameInLanguages] instead.

lib/src/model/product_type.dart

@@ -0,0 +1,32 @@
+import 'package:json_annotation/json_annotation.dart';
+import 'off_tagged.dart';
+import '../prices/flavor.dart';
+import '../utils/server_type.dart';
+
+/// Type used at the [Product] level (e.g. "this is a pet food product").
+///
+/// Somehow redundant with [ServerType] and [Flavor].
+enum ProductType implements OffTagged {
+  @JsonValue('food')
+  food(offTag: 'food'),
+
+  @JsonValue('beauty')
+  beauty(offTag: 'beauty'),
+
+  @JsonValue('petfood')
+  petFood(offTag: 'petfood'),
+
+  @JsonValue('product')
+  product(offTag: 'product');
+
+  const ProductType({
+    required this.offTag,
+  });
+
+  @override
+  final String offTag;
+
+  /// Returns the first [ProductType] that matches the [offTag].
+  static ProductType? fromOffTag(final String? offTag) =>
+      OffTagged.fromOffTag(offTag, ProductType.values) as ProductType?;
+}