Constructs a header value configured from this instance.
This value is used for the 'Cache-Control' header.
Source
String get headerValue { if (preventCaching) { return "no-cache, no-store"; } var items = []; if (preventIntermediateProxyCaching) { items.add("private"); } else { items.add("public"); } if (expirationFromNow != null) { items.add("max-age=${expirationFromNow.inSeconds}"); } if (requireConditionalRequest) { items.add("no-cache"); } return items.join(", "); }