feat: cookie SameSite property

More information:
https://tools.ietf.org/html/draft-ietf-httpbis-cookie-same-site-00#section-4.1.1
https://web.dev/samesite-cookies-explained/

src/meta/configs.js

@@ -164,6 +164,9 @@ Configs.cookie = {
 			cookie.path = relativePath;
 		}
 
+		// Ideally configurable from ACP, but cannot be "Strict" as then top-level access will treat it as guest.
+		cookie.sameSite = 'Lax';
+
 		return cookie;
 	},
 };