void Save()
{
var onlyJournalEntries = journalEntries.Select(p => p.Value);
var json = JsonConvert.SerializeObject(new PackageData(onlyJournalEntries, Cache));
fileSystem.EnsureDirectoryExists(Path.GetDirectoryName(journalPath));
//save to temp file first
var tempFilePath = $"{journalPath}.temp.{Guid.NewGuid()}.json";
fileSystem.WriteAllText(tempFilePath, json, Encoding.UTF8);
fileSystem.OverwriteAndDelete(journalPath, tempFilePath);
}