Fix test scenario for payment card

To check that a card has been succesfully activated after injected numbers on Payline server, best solution is to check length of "CardNumber".
Previous check on "IsSucceeded" wasn't working, as this property doesn't exist on Card object.

Following this, I also modified test immediate-contribution test scenario to use a more natural user flow (1. create user, 2. create card, 3. create immediate-contribution)