Like contributed modules, dependencies of a custom module can also be installed by providing a composer.json file in the directory of the custom module.
When you're, like me, using Windows as your development environment, letting your Drupal environment send mails can be a big challenge. In contrast to a Linux/Mac OS X based system, where it is much easier to send mails.
Often when already existing pages/forms have to be changed, you use one of the alter hooks to add the needed extra functionality. However, sometimes you want or are forged, to overwrite an already existing page completely.