Collect consent in your app

<form method="post" action="/signup">
  <!-- Your existing fields and CSRF protection belong here. -->
  <label for="marketing-opt-in">
    <input id="marketing-opt-in" type="checkbox"
      name="marketing_opt_in" value="yes">
    Email me occasional product updates and offers from Acme.
    I can unsubscribe anytime.
  </label>
  <a href="/privacy">How Acme uses your information</a>
  <button type="submit">Create account</button>
</form>

// Node.js 24+, server-side only.
// NOTIFICATIONS_ORIGIN is your Notifications public API origin,
// for example https://notifications.bytefoundry.co.in.
// NOTIFICATIONS_API_KEY needs contacts:write in your workspace.
async function syncSignupContact({ email, name, marketingOptIn }) {
  const origin = process.env.NOTIFICATIONS_ORIGIN;
  const apiKey = process.env.NOTIFICATIONS_API_KEY;
  if (!origin || !apiKey) throw new Error("Configure Notifications on the server");

  const payload = { email, name };
  if (marketingOptIn === true) {
    payload.marketing_consent = true;
    // Server-owned identifier for the actual form and wording version.
    payload.consent_source = "signup-form:marketing-email:v1";
  }

  const response = await fetch(new URL("/v1/contacts", origin), {
    method: "POST",
    headers: {
      Authorization: "Bearer " + apiKey,
      "Content-Type": "application/json",
    },
    body: JSON.stringify(payload),
    signal: AbortSignal.timeout(8000),
  });
  if (!response.ok) {
    throw new Error("Notifications contact sync failed: HTTP " + response.status);
  }
  return (await response.json()).data;
}

// Inside your server's form handler, after validating the customer:
// const contact = await syncSignupContact({
//   email: customer.email,
//   name: customer.name,
//   marketingOptIn: formData.get("marketing_opt_in") === "yes",
// });