Assing only cards to users

[tiotrom]

Is your feature request related to a problem? Please describe.
At times I want to assign a single card to users to look at and contribute to it (comments, description, attachments), and not share the entire deck.

Describe the solution you'd like
Assign card to users - and only that card will be visible to them. Will hide all of the other cards.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[juliushaertl]

duplicate of #663