Handle failing API calls

For `cuddlers:registerMom` I assume the only thing that can go wrong is if the user is already registered. I need to cover other cases. In the test, I need to test that the error message is logged.

For `cuddlers:addBaby:registerBaby` I need to simulate an invalid request (e.g. by passing gibberish to the API), and also test that an error has been logged.