Include staging pod on the build server

[smashwilson]

Include a content-service and presenter pair on the build server that's configured to act as a staging server. Terminate TLS at an nginx-pod container. Point a CLB at the nginx-pod entry point with a default domain of staging.{{ domain }}.

Remaining work:

• [x] Fix up the restart action.
• [x] Consolidate certificates. It's easier to get build. as an SAN on the "one true" certificate than it is to manage a bunch of different certificates.
• [x] Update the documentation to include the staging services in architecture diagrams and to discuss the staging process.

[smashwilson]

Staging environment is :ok_hand: on deconst.horse!

https://staging.deconst.horse/my-revision/