Completes validation per the story requirements

@benlovell what do you think to use a different method to test this validations? (e.g https://github.com/bcardarella/valid_attribute)

Imho, It's better to test against the error in the specific field rather than the be_valid and not be_valid because this assumption relies more on the valid factories than the valid spec itself.

But even with that, the PR is ok :+1: :+1:, but I would like to add some discussion to it, :),