resource: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#The_HTTP_request_headers
- web applications makes a CORs request when it requests a resource that has a different origin (domain, protocol, port) then its own origin.
- CORS is for security reasons, browsers restrict cross-origin HTTP requests initiated within scripts
- HTTP Header that allows servers to describe the set of origins that are permitted to read that information using a web browser.
- HTTP requests that can cause side-effects on server's data, browser must pre-flight the request (HTTP OPTIONS method), After approval, the server will send the actual request back to the browser.
- Allowed Methods:
- GET
- HEAD
- POST