Middleware: Filtering Requests Before Controllers

Middleware allows you to run logic before or after a request reaches your controller.

  Common use cases:
  - Check if user is logged in
  - Verify roles or permissions
  - Log requests
  - Add headers
  
  ## Built-in example
  
  ```php
  Route::get('/dashboard', function () {
    return view('dashboard');
  })->middleware('auth');
  ```
  
  ## Create custom middleware
  
  ```bash
  php artisan make:middleware IsAdmin
  ```
  
  ```php
  public function handle($request, Closure $next) {
    if (!auth()->user()?->is_admin) {
      abort(403);
    }
    return $next($request);
  }
  ```
  
  ## Middleware flow
  
  ```mermaid
  flowchart LR
    A[Request] --> B[Middleware]
    B --> C[Controller]
    C --> D[Response]
    D --> B
  ```
  
  Middleware keeps your controllers focused on business logic.
  
  In the next tutorial, we will decouple logic using events and listeners.