Slugs should only be updated on certain conditions, we need a trait that
meets that conditions and the name of the trait passed as a mandatory &
named argument on the sluggable concern
Before Budget.current could return multiple budgets, now there can only
be a single current_budget.
Adding the concept of open, which better reflects what the admin sees
in this page: A tab for open budgets and a tab for finished budgets
When there was only one budget this implementation worked fine
Nowadays there can be multiple budgets, and therefore the definition of
the current_budget has changed. It is no longer a budget that has not
finished, but rather, the last budget created that is not in the
initial drafting phase.
Budgets in the drafting phase are not considered the current_budget,
but rather a budget that is still being prepared and that soon will
become the current_budget
Why:
* Slug must be unique among:
1. Budget slug: among other budgets
2. Group slug: among other groups from its budget
3. Heading slug: among other headings from all the groups from its budget
How:
* Adding checks for all possible scenarios on each model specs
Why:
* Those classes have a slug attribute that needs to be filled
How:
* Just adding the shared example to Budget model spec, and creating the model spec file for Heading and Group to include it as well
