Make env vars more palatable for containerization (#10895)

* refactor(env-vars): remove object/colon syntax

* fix(tests): correct config expectations

website/server/controllers/top-level/dataexport.js

@@ -17,7 +17,7 @@ import {
   S3,
 } from '../../libs/aws';
 
-const S3_BUCKET = nconf.get('S3:bucket');
+const S3_BUCKET = nconf.get('S3_BUCKET');
 
 const BASE_URL = nconf.get('BASE_URL');