code: private static String getClientId(Map<String, Object> params, RequestOptions options)
        throws AuthenticationException {
      String clientId = Stripe.clientId;
      if ((options != null) && (options.getClientId() != null)) {
        clientId = options.getClientId();
      }
      if ((params != null) && (params.get("client_id") != null)) {
        clientId = (String) params.get("client_id");
      }
  
      if (clientId == null) {
        throw new AuthenticationException(
            "No client_id provided. (HINT: set client_id key using 'Stripe.clientId = <CLIENT-ID>'. "
                + "You can find your client_ids in your Stripe dashboard at "
                + "https://dashboard.stripe.com/account/applications/settings, "
                + "after registering your account as a platform. See "
                + "https://stripe.com/docs/connect/standard-accounts for details, "
                + "or email support@stripe.com if you have any questions.",
            null, null, 0);
      }
  
      return clientId;
    }
docs: Returns the client_id to use in OAuth requests.
  
  @param params  the request parameters.
  @param options the request options.
  @return the client_id.