private void Process(CreateAtomDocumentCommand createDocument)
        {
            var createdEvent = new AtomDocumentCreatedEvent(
                createDocument.Title,
                createDocument.Author,
                createDocument.DocumentId);

            Persist(createdEvent, MutateInternalState);
        }
        private void Process(CreateAtomDocumentCommand createDocument)
        {
            subscriptionActor = Context.Sender;

            var createdEvent = new AtomDocumentCreatedEvent(
                createDocument.Title,
                createDocument.Author,
                createDocument.DocumentId);

            Persist(createdEvent, MutateInternalState);
        }