Add Webhook and Event Notifications for OpenAI Moderation Timeouts and Failures

Introduce dedicated webhook/event support for OpenAI moderation timeouts and failures, independent of the configured fallback behavior (Approve or Deny). Currently, when the moderation fallback is set to Approve, messages are delivered even if the OpenAI moderation request times out or fails, and no webhook or notification is generated. This prevents developers from detecting moderation outages, monitoring service health, or triggering operational alerts. The requested enhancement is to expose OpenAI moderation failures through a dedicated webhook or include failure metadata in existing webhooks regardless of the fallback action. This would enable applications to monitor moderation reliability, integrate with alerting systems, and respond appropriately to prolonged OpenAI service disruptions without negatively impacting the end-user experience.