Unable to assign more certificates to a user or to a virtual card

[Jakuje]

The current design assigns 1:1:1 user, virtual card and certificate.

Some of the tests depend on selection of smart cards (using uri) or selection of certificates from a card (through user action) so before designing and implementing a lot of stuff on top of this, it would be great to decouple these objects from each other and provide 1:n relations to cover these test cases.

This will also be needed before implementing suport for removinator, which also has several cards with several certificates.