KAN-701 fix : 인증용 고객조회 API 수정

src/main/java/com/yeonieum/productservice/domain/customer/service/CustomerService.java

@@ -67,7 +67,7 @@ public int retrieveDeliveryFee(Long customerId) {
      */
     @Transactional
     public CustomerResponse.OfRetrieveForAuth retrieveCustomerForAuth(String businessNumber) {
-        Customer targetCustomer = customerRepository.findByStoreBusinessNumber(businessNumber)
+        Customer targetCustomer = customerRepository.findById(Long.valueOf(businessNumber))
                 .orElseThrow(() -> new CustomerException(CUSTOMER_NOT_FOUND, HttpStatus.NOT_FOUND));
 
         return CustomerResponse.OfRetrieveForAuth.convertedBy(targetCustomer);