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.
This way blind screen reader users will know which proposal they're
supporting. In a list of proposals, context might not be clear when a
link saying "Support" or "Support this proposal" is announced, but a
link saying "Support Create a monthly transport ticket" is less
ambiguous.
Just like we did with investments in commit de436e33a, we're keeping the
title attribute because when visiting a proposal page, the connection
between the "Support" link and the proposal is not as clear as it is in
the proposals index page, so it might not be clear what you're
supporting.
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.
The action and the views were almost identical, with the supports
progress and the HTML classes of the success message element being the
only exceptions; we can use CSS for the styles instead.
Just like we did in commit 0214184b2d for investments, we're removing
some possible optimizations (we don't have any benchmarks proving they
affect performance at all) in order to simplify the code.
The investement votes component `delegate` code was accidentally left
but isn't used since commit 0214184b2, so we're removing it now that
we're removing the `voted_for?` helper method.
