When returning a collection of records in the API, we were making sure
we only returned public ones. However, when returning individual
records, we were not checking that.
In practice, this wasn't a big issue, since most `public_for_api`
methods return all records, but it could affect Consul Democracy
installations which might have customized their `public_for_api` method.
The only exception was the `budget` method, since it was returning
budgets that were still in drafting.
Back in commit c984e666f, we reorganized the code related to the GraphQL
API, but we didn't reorganize the tests.
So we're doing it now, since we're going to fix a potential issue and
add some tests for it.
