Make `ValidationFailed` throwable without rules

[NeoIsRecursive]

Description

Perhaps a bad title, but I think this would be nice to have (standardizing "failure" responses in tempest apps).

For example, here, where the request validations passed, but we need to do additional "validation":

#[Post('/webauthn/authenticate')]
public function authenticate(AuthenticatePasskeyRequest $request, Authenticator $authenticator)
{
   // some deserialization and other logic

    $passkey = query(Passkey::class)->find(credential_id: $publicKeyCredential->rawId)->first();

    if (!$passkey) {
        // here id like to throw a validation exception
    }

In laravel there is the ValidationException::withMessages() which is what I am missing I suppose. It is possible to do something like that with ValidationFailed but it requires a lot of boilerplate + a rule to make the message.

throw new ValidationFailed([
    'answer' => [
        new FailingRule(rule: new MessageRule('Passkey not valid')),
    ],
]);

//

final readonly class MessageRule implements Rule, HasErrorMessage
{
    public function __construct(
        private string $message,
    ) {}

    public function isValid(mixed $value): bool
    {
        return false;
    }

    public function getErrorMessage(): string
    {
        return $this->message;
    }
}

Perhaps this is fine, and all that is needed is some GenericRule that takes a message?

(Another thing I found when testing this is that Validator::getErrorMessage doesn't check the HasErrorMessage if the rule is in a FailingRule)

Or is there a better way to handle these cases that I am missing?