Fix FormatModel class to work with keyless Pivot models

[Cellard]

We have two models with pivot between. It is very important for the case, that pivot has no primary key, driven with custom intermediate model and contains extra attributes:

class GameTeamPivot extends Pivot
{
    //
}

class Team extends Model 
{
    public function games(): BelongsToMany
    {
        return $this->belongsToMany(Game::class)
            ->using(GameTeamPivot::class)
            ->as('playing')
            ->withPivot('side', 'goals', 'players');
    }
}

As pivot has model, it generates events, that observes by Telescope.

In case then we update pivot attributes values, the updated event fires. And Telescope throws an Exception:

The attribute [id] either does not exist or was not retrieved for model [App\Models\Pivots\GameTeamPivot]. {"exception":"[object] (Illuminate\\Database\\Eloquent\\MissingAttributeException(code: 0): The attribute [id] either does not exist or was not retrieved for model [App\\Models\\Pivots\\GameTeamPivot]. at /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php:474)
[stacktrace]
#0 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php(454): Illuminate\\Database\\Eloquent\\Model->throwMissingAttributeExceptionIfApplicable('id')
#1 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(1954): Illuminate\\Database\\Eloquent\\Model->getAttribute('id')
#2 /Users/pm/www/fcz/press/vendor/laravel/telescope/src/FormatModel.php(17): Illuminate\\Database\\Eloquent\\Model->getKey()
#3 /Users/pm/www/fcz/press/vendor/laravel/telescope/src/Watchers/ModelWatcher.php(54): Laravel\\Telescope\\FormatModel::given(Object(App\\Models\\Pivots\\GameTeamPivot))
#4 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Events/Dispatcher.php(418): Laravel\\Telescope\\Watchers\\ModelWatcher->recordAction('eloquent.update...', Array)
#5 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Events/Dispatcher.php(249): Illuminate\\Events\\Dispatcher->Illuminate\\Events\\{closure}('eloquent.update...', Array)
#6 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Concerns/HasEvents.php(189): Illuminate\\Events\\Dispatcher->dispatch('eloquent.update...', Array)
#7 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(1210): Illuminate\\Database\\Eloquent\\Model->fireModelEvent('updated', false)
#8 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php(1121): Illuminate\\Database\\Eloquent\\Model->performUpdate(Object(Illuminate\\Database\\Eloquent\\Builder))
#9 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php(245): Illuminate\\Database\\Eloquent\\Model->save()
#10 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php(209): Illuminate\\Database\\Eloquent\\Relations\\BelongsToMany->updateExistingPivotUsingCustomClass(1, Array, false)
#11 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php(187): Illuminate\\Database\\Eloquent\\Relations\\BelongsToMany->updateExistingPivot(1, Array, false)
#12 /Users/pm/www/fcz/press/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Relations/Concerns/InteractsWithPivotTable.php(114): Illuminate\\Database\\Eloquent\\Relations\\BelongsToMany->attachNew(Array, Array, false)
#13 /Users/pm/www/fcz/press/app/Jobs/Offsite/GamesJob.php(105): Illuminate\\Database\\Eloquent\\Relations\\BelongsToMany->sync(Array)

As you can see, Telescope tries to format model name, calling getKey on model. But pivot has no primary key.

This PR is to fix this error, suggesting way to format keyless pivot name.