static AggregatedHttpFile of(HttpData data, long lastModifiedMillis) {
        requireNonNull(data, "data");
        return builder(data, lastModifiedMillis).build();
    }
Creates a new {@link AggregatedHttpFile} with the specified {@link HttpData} with the specified
{@code lastModifiedMillis}.

@param data the data that provides the content of an HTTP response
@param lastModifiedMillis when the {@code data} has been last modified, represented as the number of
                          millisecond since the epoch
core/src/main/java/com/linecorp/armeria/server/file/AggregatedHttpFile.java