In this chapter, we discussed many things. We saw how logging works in Drupal 8, how the mail API can be used programmatically (and extended), and how the token system can be employed to make our text more dynamic.
While going through this chapter, we also enriched our Hello World module. So, apart from understanding the theory about logging, we created our own logging channel service and logger plugin. For the latter, we decided to send out emails when log messages were of the type error. In doing this, we took a look at the mail API and how we can use it programmatically. We saw that, by default, PHP's native mail() function is used to send out emails, but we can create our own plugin very easily to use whatever external service we want—yet another great example of extensibility via plugins.
Lastly, we looked at tokens in Drupal 8. We saw what components...