anchor.diff:  browser and open the "/" URL the index method in the
   ApplicationController class will be called.
   
  -[NOTE]
  +NOTE:
   The Routes class has to implement the MangooRoutes interface to work properly.
   
   == Controllers
  
positive.code: https://commons.apache.org/proper/commons-email/userguide.html[Apache
  Commons Email documentation] on how to create the eMail objects you require.
  
  [NOTE]
  You don't have to create any SMTP configuration programmatically as shown in the
  Apache Commons Email documentation. This is all done via the application.yaml and passed to the Mailer class of your mangoo
  I/O application, so you can set your host, port, username, password and ssl usage only once.
  
negative.code: 2. Controller filters
  3. Method filters
  
  NOTE:
  Only the header and content values are merged with the response object returned from your controller.
  
  Here is an example of the AuthenticityFilter which is used for the CSRF checks.
  