https://api.drupal.org/api/drupal/core%21modules%21workspaces%21src%21EventSubscriber%21EntitySchemaSubscriber.php/8.9.x
EntitySchemaSubscriber.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21system%21tests%21modules%21entity_test_update%21src%21EventSubscriber%21EntitySchemaSubscriber.php/main
EntitySchemaSubscriber.php | Drupal API
phpdrupalapi