Missing user datasets prevent server boot

We had issues with mypod.store yesterday that prevented startup.

The issues were caused by a set of users with no db dataset but an entry in the settings dataset.
For one user, there was a key in the actors directory as well, which I had to delete. The other users did not have keys associated.

We should:
- Make the server boot even with issues in user setup.
- And on the other hand we need to
- Prevent those inconsistenies from occuring and find out how they occur
- and/or create a recovery mechanism that fixes missing dataset inconsistencies.