Adding custom fields to Carrier form

To add new fields to Carrier form you need to hook into the notification/carrier/registered action.

use BracketSpace\Notification\Defaults\Field\InputField;

add_action( 'notification/carrier/registered', function( $carrier ) {

	if ( 'email' === $carrier->get_slug() ) {
		return;
	}

	$carrier->add_form_field( new InputField( array(
		'label'      => __( 'Example Field' ),
		'name'       => 'example',
		'resolvable' => true,
	) ) );

} );

All the field data will be automatically stored and available in $carrier->data property in send() method.