Start a session

const VY_SK = process.env.VY_SK; // sk_test_… while building, sk_live_… to ship

const res = await fetch("https://trust.verifyyou.com/v3/initialize", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${VY_SK}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    verification_id: "<verification_id>",
    // where they land when done
    redirect_url: "http://localhost:3000/verified",
    // optionally link with your database
    // external_id: user.id,
    // link with a new person or external identifier
    // email: user.email,
  }),
});

if (!res.ok) {
  const { detail } = await res.json();
  // 400 one_identifier_only               send email OR phone, never both
  // 400 identifier_unrecognized           that email/phone isn't a shape we parse
  // 400 invalid_redirect_url              must be absolute, and https off localhost
  // 400 verification_requires_identifier  this check is set to "Provided by you"
  // 401 / 403                             wrong key, or a test-only field on a live key
  // 404 no_matching_verification          that verification_id isn't on your account
  // 409 link_not_active                   this check runs on invites, not on code
  throw new Error(`verifyyou initialize: ${res.status} ${detail}`);
}

// => { session_id: "…", url: "…" }
// use the session_id to run the verification on the frontend;
// a session's ttl is reasonable but not infinite
const { session_id } = await res.json();