Root Cause Analysis:

Request: req-ghi789
Timeline:
    [req-ghi789] gateway:request:POST:/orders
    [req-ghi789] gateway:response:status=500
    [req-ghi789] order:created:order_id=5002
    [req-ghi789] order:calling_payment
  → [req-ghi789] order:payment_failed  <-- ROOT CAUSE
    [req-ghi789] payment:processing
  → [req-ghi789] payment:error  <-- ROOT CAUSE
