Merge branch '6.4' into 7.0

* 6.4:
  [Validator] Missing translations for Estonian (et)
  [HttpFoundation] Prevent duplicated headers when using Early Hints
  [VarDumper] Fix configuring CliDumper with SYMFONY_IDE env var
  [Cache] improve BC with 5.4 pools
  [PhpUnitBridge][VarDumper] fix color detection
  [CI] Make sure we preserve file->header when we run sync-translations.php
  [Cache] Fix BC layer with pre-6.1 cache items
  Review validators.sl.xlf
  [Mailer][Postmark][Webhook] Don't require tag and metadata
  [Scheduler] Fix messenger receiver with no alias

RemoteEvent/PostmarkPayloadConverter.php

@@ -52,8 +52,13 @@ public function convert(array $payload): AbstractMailerEvent
         }
         $event->setDate($date);
         $event->setRecipientEmail($payload['Recipient'] ?? $payload['Email']);
-        $event->setMetadata($payload['Metadata']);
-        $event->setTags([$payload['Tag']]);
+
+        if (isset($payload['Metadata'])) {
+            $event->setMetadata($payload['Metadata']);
+        }
+        if (isset($payload['Tag'])) {
+            $event->setTags([$payload['Tag']]);
+        }
 
         return $event;
     }

Webhook/PostmarkRequestParser.php

@@ -48,8 +48,6 @@ protected function doParse(Request $request, #[\SensitiveParameter] string $secr
             !isset($payload['RecordType'])
             || !isset($payload['MessageID'])
             || !(isset($payload['Recipient']) || isset($payload['Email']))
-            || !isset($payload['Metadata'])
-            || !isset($payload['Tag'])
         ) {
             throw new RejectWebhookException(406, 'Payload is malformed.');
         }