Retrieves, populates, and processes an entity form.
EntityInterface $entity: The entity to be created or edited.
$operation: (optional) The operation identifying the form to be submitted.
$form_state: (optional) A keyed array containing the current state of the form.
A $form_state array already filled with the entity form controller.
function entity_form_submit(EntityInterface $entity, $operation = 'default', &$form_state = array()) {
$form_state += entity_form_state_defaults($entity, $operation);
$form_id = $form_state['build_info']['callback_object']
->getFormID();
drupal_form_submit($form_id, $form_state);
}