feat: multi-currency support and E2E tests for Kotlin sample

[pengying]

Summary

• Fix SDK type mismatches so the Kotlin sample compiles and runs against SDK v1.1.0
• Add multi-currency external account support (MXN, BRL, INR, GBP, PHP, EUR) with country selector dropdown
• Add source currency dropdown (USD/USDC) on the quote step
• Add "Start New Payment" button to restart the flow from the external account step
• Extract shared optText/requireText to JsonUtils.kt, deduplicate BeneficiaryFields parsing
• Add 7 Ktor server E2E tests hitting the Grid sandbox API
• Add 8 Playwright browser E2E tests driving the full React UI

Test plan

• cd samples/kotlin && ./gradlew test — 7 backend E2E tests pass
• cd samples/frontend && npm run test:e2e — 8 Playwright browser tests pass (requires backend running)
• Manual testing of all country destinations (IN, MX, BR, PH, GB, EU)
• Manual testing of USD and USDC source currencies
• Manual testing of "Start New Payment" reset flow

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
grid-flow-builder	Ready	Preview, Comment	Apr 10, 2026 6:39pm

[greptile-apps]

Greptile Summary

This PR adds multi-currency support (MXN, BRL, INR, GBP, PHP, EUR) to the Kotlin sample with a country selector dropdown, a source currency (USD/USDC) selector, and a "Start New Payment" reset button. It also fixes SDK v1.1.0 type mismatches, deduplicates optText/requireText helpers, and adds 7 backend Ktor E2E tests plus 8 Playwright browser tests covering the full payout flow.

Confidence Score: 5/5

Safe to merge — both P2 findings are minor style/UX issues that do not block correctness.

All remaining findings are P2: the 'Start New Payment' button appearing one step early is a no-op (harmless), and the misleading Playwright comment doesn't affect test correctness. The SDK type fixes, multi-currency routing, and test coverage are solid.

samples/frontend/src/App.tsx (Start New Payment button condition) and samples/frontend/e2e/payout-flow.spec.ts (stale comment)

Important Files Changed

Filename	Overview
samples/frontend/e2e/payout-flow.spec.ts	Adds 8 Playwright browser E2E tests covering the full payout flow; comment on line 44 incorrectly states the default country is IN when it is actually MX.
samples/frontend/playwright.config.ts	New Playwright config targeting port 8080 (Kotlin backend that serves pre-built React static files); previously flagged baseURL concern is a known trade-off documented in the spec file.
samples/frontend/src/App.tsx	Adds selectedCountry state, restartFromExternalAccount function, and "Start New Payment" button; button condition activeStep >= 1 shows it one step too early (no-op at the External Account step).
samples/frontend/src/steps/CreateExternalAccount.tsx	Adds COUNTRY_CONFIGS map with 6 currencies and a country selector dropdown; Math.random() in useEffect was already flagged in a prior review thread.
samples/frontend/src/steps/CreateQuote.tsx	Adds source currency dropdown (USD/USDC) and reads destination currency from COUNTRY_CONFIGS; clean implementation.
samples/kotlin/src/main/kotlin/com/grid/sample/JsonUtils.kt	Extracts optText/requireText extension functions to a shared location; behaviorally equivalent to the per-file implementations they replace.
samples/kotlin/src/main/kotlin/com/grid/sample/routes/ExternalAccounts.kt	Adds PHP and EUR account types, fixes SDK type references (e.g. UsdAccountInfo vs UsdExternalAccountInfo), deduplicates beneficiary parsing via parseBeneficiaryFields; EUR SWIFT workaround is documented inline.
samples/kotlin/src/main/kotlin/com/grid/sample/routes/Quotes.kt	Updates return type of buildQuoteSource to QuoteSourceOneOf and aligns factory method names to SDK v1.1.0; straightforward SDK migration.
samples/kotlin/src/test/kotlin/com/grid/sample/EndToEndTest.kt	Adds 7 backend E2E tests covering customer creation, external accounts (MXN, INR), validation rejections, quote creation, and a full payout flow; env var names in the docstring match Config.kt.
samples/kotlin/src/main/kotlin/com/grid/sample/GridClientBuilder.kt	Updates credential property references from gridClientId/gridClientSecret to apiTokenId/apiClientSecret to match renamed Config properties.
samples/kotlin/src/main/kotlin/com/grid/sample/routes/Customers.kt	Switches from local requiredText to shared requireText from JsonUtils; clean deduplication.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[POST /api/customers/:id/external-accounts] --> B{accountInfo present?}
    B -- No --> ERR1[400 accountInfo is required]
    B -- Yes --> C{accountType present?}
    C -- No --> ERR2[400 accountType is required]
    C -- Yes --> D{accountType value}

    D -- USD_ACCOUNT --> USD[buildUsdBeneficiary\n→ UsdExternalAccountInfo]
    D -- INR_ACCOUNT --> INR[buildInrBeneficiary\n→ InrExternalAccountInfo]
    D -- BRL_ACCOUNT --> BRL[buildBrlBeneficiary\n→ BrlExternalAccountInfo]
    D -- MXN_ACCOUNT --> MXN[buildMxnBeneficiary\n→ MxnExternalAccountInfo]
    D -- GBP_ACCOUNT --> GBP[buildGbpBeneficiary\n→ GbpExternalAccountInfo]
    D -- PHP_ACCOUNT --> PHP[buildPhpBeneficiary\n→ PhpExternalAccountInfo]
    D -- EUR_ACCOUNT --> EUR[buildEurBeneficiary\n→ EurAccount + optional swiftBic workaround]
    D -- other --> ERR3[throw IllegalArgumentException]

    USD & INR & BRL & MXN & GBP & PHP & EUR --> EA[ExternalAccountCreate\nvia GridClient]
    EA --> RES[201 Created — external account JSON]

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Prompt To Fix All With AI

This is a comment left during a code review.
Path: samples/frontend/src/App.tsx
Line: 92-99

Comment:
**"Start New Payment" button is a no-op at the External Account step**

When `activeStep === 1` (the user is already on the Create External Account step), clicking this button calls `setActiveStep(1)` and clears `externalAccountId`/`quoteId`, both of which are already `null` — so nothing actually changes. The button is most useful after an external account has been created (i.e., from step 2 onwards).

```suggestion
          {activeStep >= 2 && (
            <button
              onClick={restartFromExternalAccount}
              className="mt-6 px-4 py-2 bg-gray-700 hover:bg-gray-600 rounded text-sm font-medium text-gray-300"
            >
              Start New Payment
            </button>
          )}
```

How can I resolve this? If you propose a fix, please make it concise.

---

This is a comment left during a code review.
Path: samples/frontend/e2e/payout-flow.spec.ts
Line: 44-46

Comment:
**Stale comment: default country is MX, not IN**

The comment says the default country is `IN`, but `App.tsx` initialises `selectedCountry` to `'MX'`. The actual test assertions are correct (they explicitly select countries before checking), but the comment is misleading.

```suggestion
    // Default country is MX; switch to each and verify the textarea updates.

    // Switch to India
```

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (5): Last reviewed commit: "Merge branch 'main' into feat/sample-mul..." | Re-trigger Greptile}