refactor(http): address CURLRequest retry review feedback

- Add 504 Gateway Timeout to default retryable status codes
- Reuse stored cURL error number when throwing
- Add coverage for default 504 retry behavior

Signed-off-by: memleakd <121398829+memleakd@users.noreply.github.com>

Author: memleakd

system/HTTP/CURLRequest.php

@@ -91,7 +91,7 @@ class CURLRequest extends OutgoingRequest
         'max_retries'         => 3,
         'delay'               => 1000,
         'max_delay'           => 30_000,
-        'status_codes'        => [429, 503],
+        'status_codes'        => [429, 503, 504],
         'curl_errors'         => false,
         'respect_retry_after' => true,
     ];
@@ -980,7 +980,7 @@ protected function sendRequest(array $curlOptions = []): string
         if ($output === false) {
             $this->lastCurlError = curl_errno($ch);
 
-            throw HTTPException::forCurlError((string) curl_errno($ch), curl_error($ch));
+            throw HTTPException::forCurlError((string) $this->lastCurlError, curl_error($ch));
         }
 
         return $output;

tests/system/HTTP/CURLRequestRetryTest.php

@@ -72,6 +72,23 @@ public function testRetryIntegerRetriesDefaultStatusCodes(): void
         $this->assertSame([1.0], $this->request->getSleeps());
     }
 
+    public function testRetryIntegerRetriesDefaultGatewayTimeoutStatusCode(): void
+    {
+        $this->request->setOutputs([
+            "HTTP/1.1 504 Gateway Timeout\r\n\r\nFirst failure",
+            "HTTP/1.1 200 OK\r\n\r\nSuccess",
+        ]);
+
+        $response = $this->request->get('http://example.com', [
+            'retry'       => 1,
+            'http_errors' => false,
+        ]);
+
+        $this->assertSame(200, $response->getStatusCode());
+        $this->assertSame('Success', $response->getBody());
+        $this->assertSame([1.0], $this->request->getSleeps());
+    }
+
     public function testRetryUsesCustomStatusCodes(): void
     {
         $this->request->setOutputs([

user_guide_src/source/libraries/curlrequest.rst

@@ -402,7 +402,7 @@ The available retry settings are:
   The default is ``1000``.
 - ``max_delay``: Maximum delay in milliseconds. This caps both the configured ``delay`` and a
   valid ``Retry-After`` header. Set to ``0`` for no maximum delay. The default is ``30000``.
-- ``status_codes``: HTTP status codes that should be retried. The default is ``[429, 503]``.
+- ``status_codes``: HTTP status codes that should be retried. The default is ``[429, 503, 504]``.
 - ``curl_errors``: Whether to retry transient cURL errors. The default is ``false``.
 - ``respect_retry_after``: Whether to use a valid ``Retry-After`` header instead of the configured
   ``delay``. The default is ``true``.