Constructs a new MetadataGenerator.
\Drupal\edit\Access\EditEntityFieldAccessCheckInterface $access_checker: An object that checks if a user has access to edit a given field.
\Drupal\edit\EditorSelectorInterface $editor_selector: An object that determines which editor to attach to a given field.
\Drupal\Component\Plugin\PluginManagerInterface: The manager for editor plugins.
public function __construct(EditEntityFieldAccessCheckInterface $access_checker, EditorSelectorInterface $editor_selector, PluginManagerInterface $editor_manager) {
$this->accessChecker = $access_checker;
$this->editorSelector = $editor_selector;
$this->editorManager = $editor_manager;
}