response

Generic method that produces a custom response given with a code and a message:

    $self->response( $app, 404, 'Not Found' );

This could be used to create your own, which is separate from the standard one:

    $self->response( $app, 404, 'File missing in action' );

standard_response

Produces a standard response using the code.

    # first example can be more easily written as
    $self->standard_response( $app, 404 );