Move hosting to MOJ Cloud Platform

[gregtyler]

Problem

We currently host our documentation GitHub Pages. This is an easy host to use, but it doesn't support redirects when we move or rename pages, which is an important requirement going forward.

We already use MOJ Cloud Platform to host the staging version of the site, so know that it could also host the production version and—as it allows us to configure nginx—can support redirects.

Steps

• Update the main pipeline to deploy to our production Cloud Platform subdomain (currently unused)
• Add 301 redirects to our nginx configuration for pages that we know to have moved (search redirect_from)
• Update the DNS for design-patterns.service.justice.gov.uk to point to Cloud Platform
• Stop deploying to GitHub Pages