[Catalyst] HTML-Widget result new add_error() method

[Carl Franks]

I've added a new add_error() method to HTML-Widget-Result
Internally, this uses a new HTML-Widget-Error-Custom package

Here's an example of use from the POD.

    if ( ! $result->has_errors ) {
        my $user = $result->valid('username');
        my $pass = $result->valid('password');

        if ( ! $app->login( $user, $pass ) ) {
            $result->add_error({
                name => 'password',
                message => 'Incorrect Password',
            });
        }
    }

In this example, the $result initially contains no errors. If the login()
is unsuccessful though, add_error() is used to add an error to the password
Element. If the user is shown the form again using $result->as_xml(),
they will be shown an appropriate error message alongside the password
field.

[snip]

With regards to this - I think if an error is added to, say field 'foo',
then $result->valid('foo') should return undef.

I think it would be strange that both these could return true:
$result->valid('foo')
$result->has_errors('foo')

Any disagreements?

Cheers,
Carl