Fix CORS header caching in GraphQL responses (#896)

Ensure that that dynamic Access-Control-Allow-Origin header is not cached.

- Remove Access-Control-Allow-Origin header before saving to cache
- Add Access-Control-Allow-Origin dynamically when serving cached responses
  based on the incoming request's Origin

This resolves issues with CORS headers being cached alongside GraphQL
responses, which could cause incorrect Access-Control-Allow-Origin values
for clients with different origins.

doc/10_GraphQL/10_Events.md

@@ -230,6 +230,8 @@ class GraphQlSubscriber implements EventSubscriberInterface
 - `OutputCacheEvents::PRE_LOAD`: is triggered before trying to load an entry from cache, if cache is enabled. You can disable the cache  for this request by setting `$event->setUseCache(false)`. If you disable the cache, the entry won't be loaded nor saved
 - `OutputCacheEvents::PRE_SAVE`: if cache is enabled, it's triggered before saving an entry into the cache. You can use it to modify the response before it gets saved.
 
+Uncacheable headers, such as CORS Access-Control-Allow-Origin, are removed from the response before the PRE_SAVE event and re-added after the cached response is loaded.
+
 ```php
 <?php
 

src/Controller/WebserviceController.php

@@ -225,17 +225,7 @@ public function webonyxAction(
             ];
         }
 
-        $origin = '*';
-        if (!empty($_SERVER['HTTP_ORIGIN'])) {
-            $origin = $_SERVER['HTTP_ORIGIN'];
-        }
-
         $response = new JsonResponse($output);
-        $response->headers->set('Access-Control-Allow-Origin', $origin);
-        $response->headers->set('Access-Control-Allow-Credentials', 'true');
-        $response->headers->set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
-        $response->headers->set('Access-Control-Allow-Headers', 'Origin, Content-Type, X-Auth-Token');
-
         $this->cacheService->save($request, $response);
 
         return $response;

src/Service/OutputCacheService.php

@@ -71,7 +71,12 @@ public function load(Request $request)
 
         $cacheKey = $this->computeKey($request);
 
-        return $this->loadFromCache($cacheKey);
+        $response = $this->loadFromCache($cacheKey);
+        if ($response) {
+            $this->addCorsHeaders($response);
+        }
+
+        return $response;
     }
 
     /**
@@ -81,15 +86,43 @@ public function load(Request $request)
     public function save(Request $request, JsonResponse $response, $extraTags = []): void
     {
         if ($this->useCache($request)) {
-            $cacheKey = $this->computeKey($request);
             $clientname = $request->attributes->getString('clientname');
             $extraTags = array_merge(['output', 'datahub', $clientname], $extraTags);
 
+            $this->removeCorsHeaders($response);
+            $cacheKey = $this->computeKey($request);
+
             $event = new OutputCachePreSaveEvent($request, $response);
             $this->eventDispatcher->dispatch($event, OutputCacheEvents::PRE_SAVE);
 
-            $this->saveToCache($cacheKey, $event->getResponse(), $extraTags);
+            $this->saveToCache($cacheKey, $response, $extraTags);
+
+            $this->addCorsHeaders($response);
+        }
+    }
+
+    /**
+     * Removes CORS headers including Access-Control-Allow-Origin that should not be cached.
+     */
+    protected function removeCorsHeaders(JsonResponse $response): void
+    {
+        $response->headers->remove('Access-Control-Allow-Origin');
+        $response->headers->remove('Access-Control-Allow-Credentials');
+        $response->headers->remove('Access-Control-Allow-Methods');
+        $response->headers->remove('Access-Control-Allow-Headers');
+    }
+
+    protected function addCorsHeaders(JsonResponse $response): void
+    {
+        $origin = '*';
+        if (!empty($_SERVER['HTTP_ORIGIN'])) {
+            $origin = $_SERVER['HTTP_ORIGIN'];
         }
+
+        $response->headers->set('Access-Control-Allow-Origin', $origin);
+        $response->headers->set('Access-Control-Allow-Credentials', 'true');
+        $response->headers->set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
+        $response->headers->set('Access-Control-Allow-Headers', 'Origin, Content-Type, X-Auth-Token');
     }
 
     /**