Feat/lambda basic auth on dev and stage

[awdem]

This PR:

• Makes an explicit API gateway resource to replace the implicitly created one
• Adds a basic auth lambda authorizer to the API gateway in development and staging environments

Tested by deploying to dev. There should be no downtime. After merge and deploy, I will need to deploy the API from the console for dev and staging to apply the changes I made.

Part of larger project: https://app.asana.com/0/1204880927741389/1208294218492449/f

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