The `use_helpers` method was added in ViewComponent 3.8.0, and it's
included by default in all components since version 3.11.0.
Note we sometimes delegated the `can?` method to the controller instead
of the helpers, for no particularly reason. We're unifying that code as
well.
We were using the same logic six times regarding when we should show a
"participation not allowed" message. Since we're going to change the
current behavior, we're unifying the logic in one place so the changes
will be easier.
Note we're using the `budgets.investments.investment.add_label` and
`budgets.ballots.show.remove_label` internationalization keys so they're
consistent with the `budgets.investments.investment.add` and
`budgets.ballots.show.remove` keys which were already present. We aren't
unifying these keys in order to keep existing translations.
This way we can make the view code a bit easier to read.
We're also changing the order of the conditions a little bit so we only
check for the presence of a current user once.
To make sure we aren't breaking anything with these changes, we're
adding some tests. We're also replacing one system test checking content
with a component test, since component tests are much faster.
