[codex] Fix invoice pay outcome precedence

[midagedev]

Summary

Fix invoice pay handling so payment_method and source remain payment method inputs only. Explicit outcome/billtap_outcome still override when requested, but a configured invoice-backed PaymentIntent outcome now wins over an arbitrary submitted payment method ID.

Root cause

The /v1/invoices/{id}/pay handler copied the submitted payment method into InvoicePaymentOptions.Outcome. That bypassed customer/default PaymentIntent outcome metadata for manual invoice-backed payments and turned declined or action-required fixture paths into successful payments.

Validation

• go test ./internal/api -run TestInvoiceBackedOneTimePaymentFlow -count=1 -v
• go test ./internal/api ./internal/billing ./internal/storage
• go test ./...
• git diff --check

[claude]

APPROVE

Summary

이 PR은 /v1/invoices/{id}/pay 요청에서 payment_method 파라미터가 fixture-configured PaymentIntent outcome을 우선하여 덮어쓰던 문제를 올바르게 수정합니다.

Analysis

변경 영역

api.go에서 기존에 paymentMethodID를 그대로 Outcome 필드에 전달하던 로직을 명시적인 outcome/billtap_outcome 파라미터만 확인하도록 변경했습니다.

// 변경 전
outcome := paymentMethodID

// 변경 후  
Outcome: p.first("outcome", "billtap_outcome"),

이는 payManualInvoice의 outcome 결정 우선순위와 일치합니다:

1. 명시적 opts.Outcome
2. PaymentIntent metadata의 configured outcome
3. Customer-level default outcome
4. opts.PaymentMethodID (fallback)
5. "payment_succeeded" (default)

검증

TestInvoiceBackedOneTimePaymentFlow에 payment_method 파라미터를 전달하면서 configured outcome이 우선함을 검증하는 assertion을 추가했습니다:

if failed.Metadata["billtap_last_invoice_payment_outcome"] != "card_declined" {
    t.Fatalf("failed invoice metadata = %#v, want configured outcome to win over payment_method", failed.Metadata)
}

Safety 확인

• Real payment data 처리 없음: outcome 시뮬레이션만 처리
• Webhook 영향 없음
• Fixture isolation 유지
• Production boundary 관련 변경 없음

Release gate

CI에서 Release gate가 SUCCESS로 표시되어 있습니다.

Conclusion

이 변경은 billing state correctness 관점에서 올바른 수정입니다. fixture-seeded configured outcome이 arbitrary payment_method보다 우선하도록 하는 것이 Billtap의 deterministic billing simulation 의도에 부합합니다.

Blocking issue가 없으므로 APPROVE합니다.

_{Reviewed by Z.ai GLM via Claude Code Action}