public Backend(IServerApi serverApi, DDatabaseInfo databaseInfo, IMessagesApi messagesApi, IChangesetUploader changesetUploader)
{
_serverApi = serverApi;
_databaseInfo = databaseInfo;
_messagesApi = messagesApi;
_changesetUploader = changesetUploader;
_metadata = _serverApi.GetMetadata(databaseInfo.MetadataVersion);
_types = _metadata.Types.ToDictionary(k => k.Id, v => v);
_currentPerson = databaseInfo.Person;
}