Prevent Duplication Registration of Users

[noce2]

As shown in #44, the integration tests repeatedly register users with the same id prior to each test. In reality, this should not be possible. The scope of this issue is to do 2 things:

• Prevent the registration of a new user with exactly the same Id as a previous user
• Modify the integration tests so that during the @Background step, the new user is created with a random UUID which is supplied to subsequent steps