Errores OAuth

{
  "error": "invalid_grant",
  "error_description": "Authorization code has expired or was already used"
}

https://mi-app.com/oauth/callback?
  error=access_denied
  &error_description=El+usuario+canceló+el+consentimiento
  &state=VALOR_STATE_ORIGINAL

async function callWithRetry(fn, maxAttempts = 4) {
  for (let attempt = 0; attempt < maxAttempts; attempt++) {
    try {
      return await fn();
    } catch (err) {
      if (err.status !== 429 && err.status !== 503) throw err;

      const retryAfter = err.headers?.get("Retry-After");
      const waitMs = retryAfter
        ? Number(retryAfter) * 1000
        : Math.pow(2, attempt) * 500;

      await new Promise((r) => setTimeout(r, waitMs));
    }
  }
  throw new Error("Max retry attempts exceeded");
}

async function refreshAccessToken(refreshToken) {
  const res = await fetch("https://app.whatalo.com/oauth/token", { ... });
  const data = await res.json();

  if (data.error === "invalid_grant") {
    // Token family revoked — user must re-authorize
    clearStoredTokens();
    redirectToAuthorizationFlow();
    return;
  }

  if (!res.ok) throw new Error(data.error_description);
  return data;
}