Support policy responses to allow developers to return custom messages when authorization fails

[lindyhopchris]

At the moment in our authorizer class we do this:

return $this->gate->check(
    'view',
    $model
);

An improvement would be to support Policy Responses so that the developer can return authorization messages from their policy.

To do that, the code would be something like this:

$response = $this->gate->inspect(
    'view',
    $model
);

if ($response->message()) {
    $response->authorize();
}

return $response->allowed();

I.e. if the authorization response has a message, calling the authorize() method on the response will throw an authorization exception with that message if the authorization has failed.

[BenWalters]

When returning the Response::deny() function from within a policy it appears not to be respected by this package at the moment.
If I provide a code, e.g. Response::deny(code: 404) from my policy the user still gets a 403.
I think I've traced it back to the Authorizer class in that it runs check and not inspect (https://laravel.com/docs/9.x/authorization#policy-responses).

My current workaround for this is just to abort(404) but it seems a bit ugly and with the introduction of this - laravel/framework#43097 - it seems there is also good reason to use the Response class instead of abort.
Further there is now a function to denyAsNotFound() which also sets the status for you.

[haddowg]

see #298

[lindyhopchris]

Will be released in 5.0.0.