So now we test in depth at the model level, and can be a bit more
relaxed about integration tests for translations.
Note we're defining some extra factories to make sure all translatable
attributes with presence validation rules are mandatory. This way we can
simplify the way we obtain required fields, using `required_attribute?`.
Otherwise, fields having an `unless` condition in their presence
validation rules would count as mandatory even when they're not.
Create a new Budget::Phase model that:
* Stablishes a relation with its budget
* Stablishes relation with two other Budget::Phases (previous and next)
* Validates basic dates range, kind and description rules.
* Adds scopes to get the ones enabled as well as each individual phase
Create a factory that generates a basic and valid Budget::Phase
Create a model spec that checks kind, date range and budget validations.
