title: magento2 add discount to quote from custom rest api
body: <p>I have used this example to create a custom api for updating quote by rest: <a href="https://www.thirdandgrove.com/creating-custom-rest-api-magento2" rel="nofollow noreferrer">https://www.thirdandgrove.com/creating-custom-rest-api-magento2</a></p>
  
  <p>Also I have found this example to add discount to quote: 
  <a href="https://webkul.com/blog/set-custom-discount-fee-cart-magento-2/" rel="nofollow noreferrer">https://webkul.com/blog/set-custom-discount-fee-cart-magento-2/</a></p>
  
  <p>How to combine this examples to add discount to magento2 quote by custom rest api?</p>