Magento 2 Custom Rest Api

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
  <module name="Oodles_Module">
  </module>
</config>

<?php
  \Magento\Framework\Component\ComponentRegistrar::register(
      \Magento\Framework\Component\ComponentRegistrar::MODULE,
      'Oodles_Module',
      __DIR__
  );

<?php
namespace Oodles\Module\Api;
 
interface ApiInterface
{

<?php
namespace Oodles\Module\Model;

use Oodles\Module\Api\ApiInterface;
use Magento\Checkout\Model\Session;
use Magento\Quote\Model\QuoteRepository;

class AllApiModal implements ApiInterface
{
    protected $_resourceConnection;
    protected $scopeConfig;
    protected $_sessionFactory;

    public function __construct(
        \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
        \Magento\Framework\App\ResourceConnection $resourceConnection,
        Session $checkoutSession,
        \Magento\Customer\Model\Session $sessionFactory,
        QuoteRepository $quoteRepository
    )
    {
        $this->_resourceConnection = $resourceConnection;
        $this->scopeConfig = $scopeConfig;
        $this->_sessionFactory = $sessionFactory;
        $this->checkoutSession = $checkoutSession;
        $this->quoteRepository = $quoteRepository;
    }
    
    public function updateSurplus($surplus=0) {
        
        $quoteId = $this->checkoutSession->getQuoteId();
        $quote = $this->quoteRepository->get($quoteId);
        $sessionManager = $this->_sessionFactory;
        $custId = $sessionManager->getCustomerId();
        $userAuthData = $this->userAuthData($custId);
        $quote->setSurplusUsed($surplus);
        $quote->setAuthCode($userAuthData["value"]);
        $quote->save();
    }
}