https://www.w3.org/wiki/CORS_Enabled
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#preflighted_requests
    https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors
    https://stackoverflow.com/questions/46904400/why-does-the-browser-send-an-options-request-even-though-my-frontend-code-is-jus

https://enable-cors.org/

books
CORS in action

2023
https://eli.thegreenplace.net/2023/introduction-to-cors-for-go-programmers/
2022
https://dev.to/jpomykala/what-is-cors-11kf
    https://habr.com/ru/companies/otus/articles/706908/
https://forums.appgyver.com/t/cors-error-using-previewer-web-app/10200/25
    ! a lot of sniffing from WebDev
2021
https://developer.okta.com/blog/2021/08/02/fix-common-problems-cors