:recycle: go back to the way it was before

backend/lib/services/user.js

 // Configuration for Brevo
 const Brevo = require('@getbrevo/brevo')
 const apiInstance = new Brevo.TransactionalEmailsApi()
-const apiKey = apiInstance.authentications['api-key']
+const apiKey = apiInstance.apiClient.authentications['api-key']
 apiKey.apiKey = process.env.BREVO_KEY
 const sendSmtpEmail = new Brevo.SendSmtpEmail()