Env => Use dotenv-expand

ExerciseChecker/src/app.ts

 // Read from the .env file
 // ATTENTION : This lines MUST be the first of this file (except for the path import)
 const path = require('node:path');
-require('dotenv').config({
+const myEnv = require('dotenv').config({
                                            path      : path.join(__dirname, '../.env'),
                                            DOTENV_KEY: 'dotenv://:key_bebfddf18e3dd9a0bafafe0e383313f75add1da6fbe41ea5fde51f37ef1776aa@dotenv.local/vault/.env.vault?environment=development'
                                        });
+require('dotenv-expand').expand(myEnv);
 require('./shared/helpers/TypeScriptExtensions'); // ATTENTION : This line MUST be the second of this file
 
 import ClientsSharedConfig                  from './sharedByClients/config/ClientsSharedConfig';