extension String {
    /// A namespace for the security headers' default configuration values.
    ///
    /// `Strict-Transport-Security` is intentionally absent: it is only safe over HTTPS and is
    /// "sticky" in browsers, so it stays off unless explicitly configured in production.
    public enum Security {
        /// The default `Content-Security-Policy`.
        ///
        /// Restricts every resource to the site's own origin (`default-src 'self'`), blocks plugins
        /// (`object-src 'none'`), pins the document base URL (`base-uri 'self'`), and forbids framing
        /// (`frame-ancestors 'none'`). No inline-style exception is included, so pages must link
        /// external stylesheets.
        public static let contentSecurityPolicy = "default-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'"
        /// The default `X-Content-Type-Options` (disables MIME sniffing).
        public static let contentTypeOptions = "nosniff"
        /// The default `X-Frame-Options` (forbids framing the page).
        public static let frameOptions = "DENY"
        /// The default `Referrer-Policy`.
        public static let referrerPolicy = "strict-origin-when-cross-origin"
        /// The default `Permissions-Policy` (denies access to powerful browser features a static site does not use).
        public static let permissionsPolicy = "accelerometer=(), camera=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), payment=(), usb=()"
    }
}