feat: openfoodfacts#306 - unselect product image

Impacted files:
* `api_addProductImage_test.dart`: new test about "unselect product image"
* `openfoodfacts.dart`: new method `unselectProductImage`
* `ProductImage.dart`: minor unrelated refactoring

lib/model/ProductImage.dart

@@ -148,7 +148,7 @@ class ProductImage {
   String toString() =>
       'ProductImage('
           '${field.value}' +
-      (size == null ? '' : ',size=${size.value}]') +
+      (size == null ? '' : ',size=${size.value}') +
       (language == null ? '' : ',language=${language.code}') +
       (angle == null ? '' : ',angle=${angle!.degreesClockwise}') +
       (url == null ? '' : ',url=$url') +

lib/openfoodfacts.dart

@@ -1022,4 +1022,46 @@ class OpenFoodAPIClient {
         '/' +
         filename;
   }
+
+  /// Unselect a product image.
+  ///
+  /// Typically, after that the openfoodfacts web page will _not_ show
+  /// the image as selected for this product x imagefield x language anymore.
+  /// Throws an exception if not successful.
+  /// Will work OK even when there was no previous selected product image.
+  static Future<void> unselectProductImage({
+    required final String barcode,
+    required final ImageField imageField,
+    required final OpenFoodFactsLanguage language,
+    final QueryType? queryType,
+  }) async {
+    final String id = '${imageField.value}_${language.code}';
+    final Uri uri = UriHelper.getUri(
+      path: 'cgi/product_image_unselect.pl',
+      queryType: queryType,
+      queryParameters: <String, String>{'code': barcode, 'id': id},
+    );
+
+    final Response response = await HttpHelper()
+        .doGetRequest(uri, userAgent: OpenFoodAPIConfiguration.userAgent);
+    if (response.statusCode != 200) {
+      throw Exception(
+          'Bad response (${response.statusCode}): ${response.body}');
+    }
+    final Map<String, dynamic> json =
+        jsonDecode(response.body) as Map<String, dynamic>;
+    final String status = json['status'];
+    if (status != 'status ok') {
+      throw Exception('Status not ok ($status)');
+    }
+    final int statusCode = json['status_code'];
+    if (statusCode != 0) {
+      throw Exception('Status Code not ok ($statusCode)');
+    }
+    final String imagefield = json['imagefield'];
+    if (imagefield != id) {
+      throw Exception(
+          'Different imagefield: expected "$id", actual "$imageField"');
+    }
+  }
 }

test/api_addProductImage_test.dart

@@ -200,5 +200,33 @@ void main() {
           // this guy is rather slow
           Duration(seconds: 90),
         ));
+
+    test('image unselect', () async {
+      const ImageField unselectedImageField = ImageField.INGREDIENTS;
+      await OpenFoodAPIClient.unselectProductImage(
+        barcode: barcode,
+        imageField: unselectedImageField,
+        language: language,
+      );
+
+      final ProductResult productResult = await OpenFoodAPIClient.getProduct(
+        ProductQueryConfiguration(
+          barcode,
+          fields: <ProductField>[ProductField.SELECTED_IMAGE],
+        ),
+      );
+      expect(productResult.product, isNotNull);
+      expect(productResult.product!.selectedImages, isNotNull);
+      for (final ProductImage productImage
+          in productResult.product!.selectedImages!) {
+        if (productImage.language == language) {
+          expect(productImage.field, isNot(unselectedImageField));
+        }
+      }
+    },
+        timeout: Timeout(
+          // this guy is rather slow
+          Duration(seconds: 90),
+        ));
   });
 }