List delivery failures

List recent delivery failures for a specific webhook endpoint.

Use this endpoint for operational triage when webhook deliveries are failing or when reliability metrics show regressions.

Query behavior:

• Supports an optional 'limit' parameter.
• If omitted, the endpoint returns up to 20 failures.
• Failures are returned in reverse chronological order (newest first).

Each failure includes:

• Response status code from the receiver endpoint.
• Response time in milliseconds.
• Failure reason.
• HAR storage key and timestamp.

Recommended incident workflow:

1. Call this endpoint to identify the latest failing attempts.
2. Open a specific failure via GET /seller/webhooks/{webhookId}/failures/{failureId}.
3. Download the HAR when needed for deep HTTP-level debugging.