Add infra integration test and CD

[rocketnova]

Like template-application-nextjs and template-application-flask, this template repo should include an integration test with template-infra.

The integration test should:

• run whenever a PR is merged to template-application-rails
• run whenever a PR is merged to template-infra
• deploy an update to an AWS account for a long-running example instance of template-application-rails

[rocketnova]

🔒 Tech spec (gdoc) ready for review.

[rocketnova]

CC @lorenyu @SammySteiner

[doshitan]

Done in 1d941fa and c90bd35