I've noticed that the developer console doesn't seem to expose anywhere where I can configure static environment variables.
Is the expectation on GAE that I will bundle those variables as part of the deployment from my build server? If so, is there any documentation on GAE/Google Cloud that covers why or details the philosophy?
Environment variables can be defined in your application's
app.yaml
An example for a python/php/(maybe go?) app. Java uses a different format.
https://cloud.google.com/appengine/docs/python/config/appconfig#Python_app_yaml_Defining_environment_variables
You can set these values during your CI process as well if you need to by programmatically appending them to your app.yaml before deploying.