private topics should be saved continously

[RobertMischke]

As a user who edits a private topic - I do not want to care about saving the document, I just what to have an autosave mechanism

how to deal with history:

• if we continuously save, we need to create some kind of checkpoints to reduce the amount of "changes"
  -- aggregate in blocks by size and session (10 edits done in short time, can be aggregated)
  -- may be implement as background process
  -- consider the behavior in the feed