fix(samples/kotlin): send customer email for USDB embedded wallets

[pengying]

The platform requires a customer email when it supports USDB embedded
wallets. Wire email through the customer create builder and add it to
the sample's default request body. The Grid API validates domain
deliverability, so the default uses a real domain (gmail.com).

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
grid-flow-builder	Ignored	Preview	Jun 26, 2026 12:17am
grid-wallet-demo	Ignored	Preview	Jun 26, 2026 12:17am

[pengying]

• fix(samples/frontend): floor default quote amount to corridor minimum #605
• fix(samples/frontend): scale default quote amount by source currency decimals #604
• fix(samples/kotlin): select crypto network when funding a quote from USDC #603
• feat(samples/kotlin): add exchange-rates lookup flow #602
• feat(samples/kotlin): add USD → USDC wallet payout flow #593
• fix(samples/kotlin): send customer email for USDB embedded wallets #590 👈 (View in Graphite)
• feat(samples/kotlin): support GRID_API_BASE_URL override #589
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Greptile Summary

This PR wires an email field through the customer creation flow for platforms that support USDB embedded wallets, which require the Grid API to validate domain deliverability via MX records.

• Frontend sample (CreateCustomer.tsx): adds an email field with a random suffix to the default JSON body, mirroring the existing platformCustomerId pattern, and includes a comment explaining the MX-validation requirement.
• Kotlin backend sample (Customers.kt): routes the email key from the incoming JSON body into CreateCustomerRequest.Individual.Builder, following the same optional-field pattern already used for fullName, nationality, and birthDate.

Confidence Score: 5/5

Safe to merge — both changes are additive, follow established patterns, and touch only sample code.

Both files make small, additive changes: the frontend adds an email field to the editable default JSON (mirroring the existing platformCustomerId random-suffix pattern), and the Kotlin route threads the email value into the builder exactly as other optional fields are handled. No logic is altered, no required fields are removed, and the gmail.com domain reliably passes MX validation.

No files require special attention.

Important Files Changed

Filename	Overview
samples/frontend/src/steps/CreateCustomer.tsx	Adds email with random suffix to DEFAULT_BODY, consistent with existing platformCustomerId pattern; comment correctly explains MX-validation requirement.
samples/kotlin/src/main/kotlin/com/grid/sample/routes/Customers.kt	Wires email from JSON body into the Individual builder using the same optional-field pattern as fullName, nationality, and birthDate.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant FE as Frontend Sample (CreateCustomer.tsx)
    participant KT as Kotlin Sample (Customers.kt)
    participant Grid as Grid API

    FE->>KT: "POST /api/customers { platformCustomerId, fullName, email, ... }"
    KT->>KT: Parse JSON body
    KT->>KT: Build Individual with platformCustomerId, fullName, email (NEW), nationality, birthDate, address
    KT->>Grid: customers.create(params)
    Note over Grid: Validates email domain MX records (required for USDB wallets)
    Grid-->>KT: Customer response
    KT-->>FE: 201 Created (JSON)

Loading

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
sequenceDiagram
    participant FE as Frontend Sample (CreateCustomer.tsx)
    participant KT as Kotlin Sample (Customers.kt)
    participant Grid as Grid API

    FE->>KT: "POST /api/customers { platformCustomerId, fullName, email, ... }"
    KT->>KT: Parse JSON body
    KT->>KT: Build Individual with platformCustomerId, fullName, email (NEW), nationality, birthDate, address
    KT->>Grid: customers.create(params)
    Note over Grid: Validates email domain MX records (required for USDB wallets)
    Grid-->>KT: Customer response
    KT-->>FE: 201 Created (JSON)

Loading

_{Reviews (3): Last reviewed commit: "fix(samples/kotlin): send customer email..." | Re-trigger Greptile}

[restamp-bot]

4019a29 is a pure rebase onto f206e35. Approving based on @jklein24's previous approval of a565834.

[restamp-bot]

4019a29 is a pure rebase onto f206e35. Approving based on @jklein24's previous approval of a565834.

[pengying]

Merge activity

• Jun 26, 12:16 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jun 26, 12:18 AM UTC: Graphite rebased this pull request as part of a merge.
• Jun 26, 12:18 AM UTC: @pengying merged this pull request with Graphite.

The base branch was changed.

[restamp-bot]

64ed903 is a pure rebase onto 2e9f36b. Approving based on @shreyav's previous approval of 4019a29.