protected BookManager::updateParent(array $link)
Sets the has_children flag of the parent of the node.
This method is mostly called when a book link is moved/created etc. So we want to update the has_children flag of the new parent book link.
Parameters
array $link: The book link, data reflecting its new position, whose new parent we want to update.
Return value
bool TRUE if the update was successful (either there is no parent to update, or the parent was updated successfully), FALSE on failu