Refactor AddressConfirmationProfile

* Remove the Manager since that can be implemented in the save() method
* Assign proper initial values for the model
* generate the activation_key using uuid4()
* Remove the 'feature' creating a duplicate profile updates the first.
  as this should be impossible. Tests exist to ensue we do that properly
* Update tests, remove the fixed activation_keys that were not used for anything

See merge request !75