Apply config changes for CSP file uploads.

This applies configuration changes for the Flask app and adds changes to
the Dockerfile so that the build can make a CSP-specific JS bundle. It
adds `write_dotenv` script that creates the appropriate `.env` file for
the `parcel` bundler depending on how the `CSP` environment variable is
set.

- Configure K8s environment variables for Flask CSP usage
- Supply default CSP config setting to Flask app
- Declare the CSP arg in the Dockerfile
- Supply extra Docker build args to CD
- Fix top-level reference to boto3 in file_upload module
- Add back missing sample NGINX config for docker-compose build

deploy/azure/atst-envvars-configmap.yml

@@ -11,3 +11,4 @@ data:
   UWSGI_CONFIG_FULLPATH: /opt/atat/atst/uwsgi.ini
   CRL_STORAGE_PROVIDER: CLOUDFILES
   LOG_JSON: "true"
+  CSP: azure