(CM-536) Content block discovery

[pezholio]

⚠️ DO NOT MERGE ⚠️

This is a proof of concept to demonstrate how we might use content blocks within the context of smart answers for Pensions. Rather than relying on the values in the YAML file (which needs changing each uprating cycle), we fetch the latest value from the Publishing API.

A couple of things to consider:

• How would we cache this value? Ideally we wouldn't want to fetch the value each time, but equally, we'd want to guarantee the new value is available at time of publication
• The way we fetch pensions and rates is a bit brittle, and relies on the naming being identical across environments - should these be stored in environment variables? Or should there be a tighter integration between Smart Answers and Content Block Manager?
• How would previewing rates work? At the moment, when values are changes in the Smart Answers repo, we spin up a new app in Heroku, but with the values being live, how would this work?
• Publishing API doesn't have a public HTTP endpoint, so this won't work in the Heroku review apps. How do we address this?

Again, this is not production ready, but I'd like to spin it up in integration and see how it works.