Allow "private" submissions

[sbjzn]

Is your feature request related to a problem? Please describe.
It would be helpful to be able to submit a sample as "private", meaning that it can only be viewed by the submitting user.

Sometimes we submit data that could contain sensitive information, and it would be good to be able to keep access to the submission as restricted as possible.

Describe the solution you'd like
In the classification dialog when submitting a sample, add a "Private" flag, which when submitted is only viewable by the submitting user.
Perhaps this can be solved by creating a classification group with the users uid as the classification group denominator and automatically adding every user to this classification group in the background.

Describe alternatives you've considered
The functionality can be solved by using the auto_properties setting in the auth provider, but that is not as pretty of a solution, would prefer this to be integrated into the platform instead.

Additional context
N/A