App Service - Allow easy environment variable addition

[cmaneu]

Overview of the issue

We should be able to easily add environment variables without modifying extensively the terraform templates (at least the modules).

Suggest a Fix

See #84 and the map(string) construct. We should also document how to do that with GitHub Actions / Secrets.

NubesGen Version(s)

0.0.1

[cmaneu]

FYI: Implemented by Bicep, still TBD for Terraform