Represents a 304 response.
Where lastModified is the last modified date of the resource
and cachePolicy is the same policy as applied when this resource was first fetched.
Source
Response.notModified(DateTime lastModified, HTTPCachePolicy cachePolicy) {
statusCode = HttpStatus.NOT_MODIFIED;
headers = {HttpHeaders.LAST_MODIFIED: HttpDate.format(lastModified)};
this.cachePolicy = cachePolicy;
}