Mailable : fixes strict comparison with int value (#45138)

Author: MikeElghali

src/Illuminate/Mail/Mailables/Envelope.php

@@ -364,6 +364,6 @@ public function hasSubject(string $subject)
      */
     public function hasMetadata(string $key, string $value)
     {
-        return isset($this->metadata[$key]) && $this->metadata[$key] === $value;
+        return isset($this->metadata[$key]) && (string) $this->metadata[$key] === $value;
     }
 }