fetchSite( request: Request,): null | "none" | "same-origin" | "cross-site" | "same-site" Returns null | "none" | "same-origin" | "cross-site" | "same-site"
fetchSite( headers: Headers,): null | "none" | "same-origin" | "cross-site" | "same-site" Returns null | "none" | "same-origin" | "cross-site" | "same-site"
See
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Sec-Fetch-Site