/**
* Generate a captcha, write the characters into $_SESSION['captcha'] and returns a real image which will be used
* like this: <img src="......./login/showCaptcha" />
* IMPORTANT: As this action is called via <img ...> AFTER the real application has finished executing (!), the
* SESSION["captcha"] has no content when the application is loaded. The SESSION["captcha"] gets filled at the
* moment the end-user requests the <img .. >
* Maybe refactor this sometime.
*/
public function showCaptcha()
{
CaptchaModel::generateAndShowCaptcha();
}