Setting environment variables securly

Documentation states that all environment variables, global or per-stage, should be set in `.chalice/config.json`.

However, assuming `config.json` is committed to source control, this is a bad practice that commit secrets to a shared project.

Setting environment variables directly through the AWS Lambda web UI is a non-solution since they will be deleted / overridden on the next `chalice deploy`.

What's the best way to store env vars in a secure way that also allows committing `config.json` to source control?

Start by reviewing the existing guidance for `.chalice/config.json` and the behavior of `chalice deploy`, then compare it with the AWS Lambda web UI workflow described in the issue. Done means documenting a secure, source-control-compatible way to provide environment variables without committing secrets, covering the relevant configuration or deployment entry point.

Written by the indexing model from the issue text.