What i had to look up to port a Drupal 7 module to Drupal 8
Some of it, anyway.
This is… sort of wrong:
https://drupal.stackexchange.com/questions/186156/drupal-8-variable-get#186160
https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Url.php/class/Url/8.6.x
How to return a renderable array (Drupal won’t accept a plain string anymore) in a controller to display a page:
$build['#title'] = 'Page not found';
$build['#markup'] = 'The requested page could not be found.';
return $build;
From https://cgit.drupalcode.org/search404/tree/src/Controller/Search404Controller.php?id=3683c2e
https://stackoverflow.com/questions/50862690/drupal-8-translatable-configuration
https://www.drupal.org/docs/8/multilingual/translating-configuration
https://www.drupal.org/docs/8/api/configuration-api/configuration-schemametadata