once the frontend app tries to send a request to the backend API, a browser makes a so-called pre-flight request to the backend API and asks about the allowed options: who is allowed to call the API and what type of requests can be sent <!DOCTYPE html> < html lang = "en" > < head > < meta charset = "UTF-8" > < meta name = "viewport" content = "width=device-width, initial-scale=1.0" > < title >Books</ title > link href = "https://cdn.jsdelivr.net/npm/ [email protected] /dist/css/bootstrap.min.css" rel = "stylesheet" integrity = "sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin = "anonymous" > script src = "https://cdn.jsdelivr.net/npm/ [email protected] /dist/js/bootstrap.bundle.min.js" integrity =…