The taxonomy tail every HTTP error mapper shares once PSP-specific codes are exhausted: 429 → rate_limited (retryable), 5xx → psp_unavailable (retryable), anything else → invalid_request (caller-side, never retried).
The taxonomy tail every HTTP error mapper shares once PSP-specific codes are exhausted: 429 → rate_limited (retryable), 5xx → psp_unavailable (retryable), anything else → invalid_request (caller-side, never retried).