Decide how to display new and old constituencies on the site

[zarino]

• Do we default to new constituencies as soon as they’re available? Or always show a disambiguation page, until the election? (My instinct is the former.)
• How should we cross-link between related new and old constituencies?
• How should we handle incumbent MPs on new constituency pages, and MP candidates on old constituency pages?
• Jake wondered whether we could have one paragraph summaries of the new constituencies, to help people understand what’s changed? Is this something that we could auto-generate? Or source from somewhere else?
• Show users when a dataset they’re looking at has been "transformed" (?) from an old constituency.

[zarino]

Current thinking on how to display this, on the Explore page…

And on the Area pages (which are going to change anyway, soon, as part of #210)…

[zarino]

This seems like a good approach. Closing this ticket now, as we’ve decided. Implementation will come in #256.