private function register_fields_for_certificate_templates() {

		register_rest_field(
			'llms_certificate',
			'certificate_title',
			array(
				'schema'          => array(
					'description' => __( 'Certificate title.', 'lifterlms' ),
					'type'        => 'string',
				),
				'get_callback'    => function( $object ) {
					$cert = llms_get_certificate( $object['id'], true );
					return $cert ? $cert->get( 'certificate_title' ) : null;
				},
				'update_callback' => function( $value, $post ) {
					$cert = llms_get_certificate( $post->ID, true );
					return $cert ? $cert->set( 'certificate_title', $value ) : null;
				},
			)
		);

		register_rest_field(
			'llms_certificate',
			'certificate_sequential_id',
			array(
				'schema'          => array(
					'description' => __( 'Next sequential ID.', 'lifterlms' ),
					'type'        => 'integer',
					'arg_options' => array(
						'validate_callback' => function( $value, $request ) {
							return (int) $value >= llms_get_certificate_sequential_id( $request['id'] );
						},
					),
				),
				'get_callback'    => function( $object ) {
					return llms_get_certificate_sequential_id( $object['id'] );
				},
				'update_callback' => function( $value, $post ) {
					$cert = llms_get_certificate( $post->ID, true );
					return $cert ? $cert->set( 'sequential_id', $value ) : null;
				},
			)
		);

	}