Show in ‘more votes screen’ when a vote for one policy is also associated with other policies

[ajparsons]

We should make it clearer on the ‘more details’ page when a vote for a policy is also related to a vote for a different policy.

E.g. we should end up with something like this:

Reasoning:

Our display suggests that MPs are voting on policies in isolation. In practice, for big votes on legislation, many different policies are related to the same vote - but they are not decided independently. MPs do not have the chance to vote for A, but not B - the final bill packages A and B together. This is in part because they are in a related area and get packaged in the same bill (e.g. a Justice bill), but doing it is also a deliberate tactic by the government to force the opposition to vote against popular things they might support independently.

There are clear problems in accurately and clearly presenting information, the more 'one vote' behind the scenes, is being presented as 'many issues' in front of the house. In practice, omnibus bills are a real problem for our current model of voting, which we resolve by not duplicating where possible, but also by just choosing to be ok with a certain amount of duplication.

The more we express this overlap in the interface, the more we can live with this problem. This requires some light data work in TheyWorkForYou, but works based on existing data and I have a draft version of this working in a branch.

A quick draft of this can be found in this branch: master...policy-page-show-intersections.

I think this approach isn’t the most optimal however, and is adding more queries than is necessary to load the page (but also, might just be fine).