try to toString

lib/helpers/api_helper.dart

@@ -52,6 +52,39 @@ class ApiHelper {
     );
   }
 
+  Future<Response> bridgeHandler(Request request) async {
+    final query = request.url.queryParameters;
+    final code = query['code'];
+    final redirectUri = query['redirect_uri'];
+
+    if (code == null || redirectUri == null) {
+      return Response(400, body: "Missing code or redirect_uri");
+    }
+
+    final tokenRes = await tokenHandler(
+      Request(
+        "POST",
+        Uri.base,
+        body: utf8.encode('code=$code&client_id=proxy'),
+      ),
+    );
+
+    if (tokenRes.statusCode != 200) {
+      return Response(400, body: "Token post failed");
+    }
+
+    final uri = Uri.parse(redirectUri).replace(
+      queryParameters: {
+        ...Uri.parse(redirectUri).queryParameters,
+        ...(json.decode(await tokenRes.readAsString()) as Map).map(
+          (key, value) => MapEntry(key, value.toString()),
+        ),
+      },
+    );
+
+    return Response.found(uri.toString());
+  }
+
   Future<Response> tokenHandler(Request request) async {
     final settings = ref.read(SettingsController.provider)!;
     final body = Uri.splitQueryString(await request.readAsString());
@@ -102,37 +135,6 @@ class ApiHelper {
     );
   }
 
-  Future<Response> bridgeHandler(Request request) async {
-    final query = request.url.queryParameters;
-    final code = query['code'];
-    final redirectUri = query['redirect_uri'];
-
-    if (code == null || redirectUri == null) {
-      return Response(400, body: "Missing code or redirect_uri");
-    }
-
-    final tokenRes = await tokenHandler(
-      Request(
-        "POST",
-        Uri.base,
-        body: utf8.encode('code=$code&client_id=proxy'),
-      ),
-    );
-
-    if (tokenRes.statusCode != 200) {
-      return Response(400, body: "Token post failed");
-    }
-
-    final uri = Uri.parse(redirectUri).replace(
-      queryParameters: {
-        ...Uri.parse(redirectUri).queryParameters,
-        ...json.decode(await tokenRes.readAsString()),
-      },
-    );
-
-    return Response.found(uri.toString());
-  }
-
   Future<Response> userinfoHandler(Request request) async {
     final auth = request.headers["authorization"];
     if (auth == null || !auth.startsWith("Bearer ")) {