private async void Authenticate(Client tentativeClient)
        {
            ErrorMessage.Text = "";
            Client authClient = await ClientAPI.Auth(tentativeClient);

            if (authClient != null)
            {
                // set as active client and change panel
                ActiveClient = authClient;
                ChangeActivePanel(MainForm.Panel.Home);
            }
            else
            {
                ErrorMessage.Text    = "Informations de connexion erronées.";
                UserTextBox.Text     = "";
                PasswordTextBox.Text = "";
                UserTextBox.Focus();
            }
        }