[5.4] Handle model instance in Authorize middleware

[shulard]

Related to #17848 issue.

This will help extending Middleware capabilities by giving it directly the Model to check.

Implementation example :

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Auth\Middleware\Authorize;

class AuthorizeCommand extends Authorize
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next, $ability = null, ...$models)
    {
        if ((null !== $command = $request->route('command')) &&
            $command instanceof Model
        ) {
            return parent::handle($request, $next, 'access', $command);
        }

        return $next($request);
    }
}