Add HttpInterceptor to HttpHelper

lib/utils/HttpHelper.dart

@@ -12,8 +12,18 @@ import '../model/User.dart';
 import 'OpenFoodAPIConfiguration.dart';
 import 'QueryType.dart';
 
+abstract class HttpInterceptor {
+  Future<http.Response>? interceptGet(
+      Uri uri, User? user, UserAgent? userAgent, QueryType? queryType);
+  Future<http.Response>? interceptPost(
+      Uri uri, Map<String, String?> body, User user, QueryType? queryType);
+  Future<Status>? interceptMultipart(Uri uri, Map<String, String> body,
+      Map<String, Uri>? files, User? user, QueryType? queryType);
+}
+
 /// General functions for sending http requests (post, get, multipart, ...)
 class HttpHelper {
+  static HttpInterceptor? interceptor;
   static final HttpHelper _singleton = HttpHelper._internal();
   factory HttpHelper() => _singleton;
   HttpHelper._internal();
@@ -31,6 +41,11 @@ class HttpHelper {
     UserAgent? userAgent,
     QueryType? queryType,
   }) async {
+    final interception =
+        interceptor?.interceptGet(uri, user, userAgent, queryType);
+    if (interception != null) {
+      return await interception;
+    }
     http.Response response = await http.get(
       uri,
       headers: _buildHeaders(
@@ -53,6 +68,11 @@ class HttpHelper {
   Future<http.Response> doPostRequest(
       Uri uri, Map<String, String?> body, User user,
       {QueryType? queryType}) async {
+    final interception = interceptor?.interceptPost(uri, body, user, queryType);
+    if (interception != null) {
+      return await interception;
+    }
+
     http.Response response = await http.post(
       uri,
       headers: _buildHeaders(
@@ -78,6 +98,12 @@ class HttpHelper {
     User? user,
     QueryType? queryType,
   }) async {
+    final interception =
+        interceptor?.interceptMultipart(uri, body, files, user, queryType);
+    if (interception != null) {
+      return await interception;
+    }
+
     var request = http.MultipartRequest('POST', uri);
 
     request.headers.addAll(