Services and dependency injection in Drupal 8
https://www.drupal.org/node/2133171
Service Container
http://symfony.com/doc/current/service_container.html
Create a custom Service
https://www.drupal8.ovh/en/tutoriels/249/create-a-custom-service
How to define an Event, Dispatcher and Subscriber in Drupal 8?
Lesson 8.1 - Services, dependency injection, and service containers
https://docs.acquia.com/article/lesson-81-services-dependency-injection-and-service-containers
Lesson 8.2 - Services and controllers
https://docs.acquia.com/articles/drupal-8-services-and-controllers
Lesson 8.3 - Dependency injection
https://docs.acquia.com/articles/drupal-8-dependency-injection
Lesson 8.4 - Conclusion and other information
https://docs.acquia.com/article/lesson-81-services-dependency-injection-and-service-containers
Drupal 8 et les événements
https://www.flocondetoile.fr/blog/drupal-8-et-les-evenements
How to Register an Event Subscriber in Drupal 8
https://www.chapterthree.com/blog/how-to-register-event-subscriber-drupal8
Responding to Events in Drupal 8
https://drupalize.me/blog/201502/responding-events-drupal-8
Drupal 8: Creating and Subscribing to Events
https://x-team.com/blog/creating-and-subscribing-to-events/
Drupal 8 Hooks and the Symfony Event Dispatcher
https://www.sitepoint.com/drupal-8-hooks-symfony-event-dispatcher/
Drupal 8: Hooks, Events, and Event Subscribers
https://www.daggerhart.com/drupal-8-hooks-events-event-subscribers/
Lesson 9.1 - Creating Elements, Theming Elements, and Managing Front-end Libraries
Lesson 9.2 - Twig
https://docs.acquia.com/articles/drupal-8-twig
Lesson 9.3 - Adding JavaScript / CSS / Libraries to components
https://docs.acquia.com/articles/drupal-8-adding-javascript-css-libraries-components
Lesson 9.4 - Advanced render array patterns
https://docs.acquia.com/articles/drupal-8-advanced-render-array-patterns