Replace Carbon types with CarbonInterface to support CarbonImmutable

[abdelhamiderrahmouni]

Some of the laravel projects prefer to work with Immutable Dates.

Date::use(CarbonImmutable::class);

and using this package while keeping this approach results in the follwoing error

 php artisan imap:watch default --with=flags,headers,body
Watching mailbox [default]...
Message received: [7]

   TypeError 

  Cannot assign Carbon\CarbonImmutable to property DirectoryTree\ImapEngine\Laravel\Commands\HandleMessageReceived::$lastReceivedAt of type ?Illuminate\Support\Carbon

  at vendor/directorytree/imapengine-laravel/src/Commands/HandleMessageReceived.php:33
     29▕         );
     30▕ 
     31▕         $this->attempts = 0;
     32▕ 
  ➜  33▕         $this->lastReceivedAt = Date::now();
     34▕ 
     35▕         Event::dispatch(new MessageReceived($message));
     36▕     }
     37▕ }

      +20 vendor frames 

  21  artisan:13
      Illuminate\Foundation\Application::handleCommand()

[stevebauman]

Thanks @abdelhamiderrahmouni! I've updated this to use CarbonInterface instead of using a union-type. Both Carbon and CarbonImmutable use this interface.

[stevebauman]

I've just released v1.1.1 with this PR included.