async function createCertificate(payload) {
  const response = await fetch('https://api.dokstamp.com/certificates', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${TOKEN}`,
      'Accept': 'application/json',
      'Content-Type': 'application/json',
      'X-Tenant': TENANT,
    },
    body: JSON.stringify(payload),
  });

  if (!response.ok) {
    const error = await response.json();

    if (response.status === 422) {
      // Validation error — inspect error.errors for field-level detail
      console.error('Validation failed:', error.errors);
    } else if (response.status === 401) {
      // Token expired or missing — request a new service token
      await renewToken();
    } else {
      throw new Error(error.message);
    }
  }

  return response.json();
}

use Illuminate\Support\Facades\Http;

$response = Http::withToken($token)
    ->withHeaders(['X-Tenant' => $tenant, 'Accept' => 'application/json'])
    ->post('https://api.dokstamp.com/certificates', $payload);

if ($response->failed()) {
    $error = $response->json();

    if ($response->status() === 422) {
        // Field-level validation errors
        foreach ($error['errors'] as $field => $messages) {
            logger()->warning("$field: " . implode(', ', $messages));
        }
    }

    throw new RuntimeException($error['message'] ?? 'API error');
}

$certificate = $response->json('data');