Make callback arguments available while building a checklist.

Attached a patch and added a change record: https://www.drupal.org/node/3077055

Made a typo in the api file.

Sure. First of all the change doesn't allow me to do anything I can't do without the patch, but in order to do so I need to rely on deprecated behavior, which for obvious reasons don't want to do ;).

Basically we've build a UI for the checklist api where certain users can create checklists on the fly by connecting a couple of custom entity types. In essence the implementation of hook_checklistapi_checklist_info look like:

function hook_checklistapi_checklist_info() {
  $info = [];
  foreach(Drupal::entityTypeManager()->getStorage('foobar')->loadMultiple() as $list) {
    $info[$list->uuid()] = [
      '#title' => $list->label(),
      '#description' => $list->getDescription(),
      '#path' => 'checklist/' . $list->id(),
      '#callback' => '_buildlistitems',
      '#callback_arguments' => [$list],
    ];
  }
}

function _buildlistitems(ListInterface $list) {
  $elements = [];

  foreach ($learning_path->elements->referencedEntities() as $element) {
    $elements[$element->uuid()] = [
      '#title' => $element->label(),
      '#description' => $element->getDescription(),
    ];
  }

  return $elements;
}

Our initial implementation has the loop defined in _buildlistitems straight in the info hook, but per the api documentation that behavior is deprecated. And since the content of the list is defined by the entity that is being converted it is needed to pass the entity through to the callback.