Configure post-deployment canary tests for relevant API endpoints

[anth-volk]

In response to https://github.com/PolicyEngine/issues/issues/30. We currently use BetterStack to run a post-deployment canary test, but only for the API as a whole. This does not help diagnose bugs within individual endpoints, which is what was present in the linked issue. This issue wasn't identified for three days, until an internal user found it.