ObserverServiceProvider.php

<?php 

namespace App\Providers;

use Illuminate\Support\ServiceProvider;
use App\Models\Quotation;
use App\Observers\QuotationObserver;

class ObserverServiceProvider extends ServiceProvider
{
    public function boot()
    {
        Quotation::observe( new QuotationObserver );
    }
    public function register()
    {
    }
}