code: function base64credentials () {
    var id = this.client.client_id
    var secret = this.client.client_secret
    var credentials = id + ':' + secret
  
    return Buffer.from(credentials).toString('base64')
  }
docs: Base64 Credentials
  
  Base64 encodes the user:password value for an HTTP Basic Authorization
  header from a provider configuration object. The provider object should
  specify a clientId and client_secret.