Not doing so has a few gotchas when working with relations, particularly
with records which are not stored in the database.
I'm excluding the related content file because it's got a very peculiar
relationship with itself: the `has_one :opposite_related_content` has no
inverse; the relation itself is its inverse. It's a false positive since
the inverse condition is true:
```
content.opposite_related_content.opposite_related_content.object_id ==
content.object_id
```
Usually when we specify a `belongs_to` relations, we also specify its
equivalent `has_many`. That allows us to write, for example:
`topic.user.topics`.
Just like we do in the Budget module, and in some places in the Poll and
Legislation modules, we don't need to specify the class name when the
name of the relation matches the name of a class in the same module.
Using `setseed` and ordering by `RAND()` doesn't always return the same
results because, although the generated random numbers will always be
the same, PostgreSQL doesn't guarantee the order of the rows it will
apply those random numbers to, similar to the way it doesn't guarantee
an order when the `ORDER BY` clause isn't specified.
Using something like `reorder("legislation_proposals.id % #{seed}")`,
like we do in budget investments, is certainly more elegant but it makes
the test checking two users get different results fail sometimes, so
that approach might need some adjustments in order to make the results
more random.
