Add healthcheck scenario for collections

[benthorner]

https://trello.com/c/epNWudCR/176-write-an-rfc-for-continuous-deployment-and-seek-review

Previously this app didn't have a healthcheck endpoint. This adds
a scenario to explicitly check the new endpoint 1 as a standard
safety check for apps that have Continuous Deployment enabled.

Testing

You should manually test your PR before merging.

This app doesn't have CI setup, and it would be misleading to do so:
the behaviour of the tests changes depending on the environment they
are run in. You should manually test in applicable environments,
until you are confident your change is not a breaking one.

Example steps to test in Integration:

• Click "Configure" for the Smokey job
• Change the "Branch specifier" to the name of your branch
• Run a new build of the Smokey project and check the results

Deployment

You need to manually deploy your PR after merging.

Steps to deploy a change:

• Run the Smokey deploy job to deploy the continuous Smokey loop
• Repeat this in Staging and Production

The manual Smokey job will pick up changes on master automatically. You only need to do a manual deployment for the continuous Smokey loop.