added relationship for invoice and booking

added confirm invoice feature (after user upload the image)

app/Booking.php

@@ -47,5 +47,11 @@ class Booking extends Model
     public function purchaseOrder(){
         return $this->hasOne(PurchaseOrder::class);
     }
+
+    public function invoice(){
+        return $this->hasOne(Invoice::class);
+    }
+
+
 }