Ajax helper traits

Two new traits have been added to assist with AJAX requests:

AjaxHelperTrait

This trait defines two methods:

• isAjax() - Returning a boolean value, isAjax() does exactly what it says. It determines if the current request is via AJAX. Then returns TRUE if the current request is via AJAX, FALSE otherwise.
• getRequestFormat() - Returning a string value, this method gets the wrapper format of the current request.

AjaxFormHelperTrait

To be used when submitting a form via AJAX this trait containts a public method and an abstract protected method:

• ajaxSubmit($form, $form_state) - This should be set as the AJAX callback on the submit button. It will flag any errors, and on a successful submission call the other method in this trait, successfulAjaxSubmit().
• successfulAjaxSubmit($form, $form_sate) - This abstract method would need to be implemented in the class which uses the trait, it's where the successful AJAX submission is responded to. It must return a \Drupal\Core\Ajax\AjaxResponse object.