add file to lan paid off letter

app/Modules/LoanPaidOffLetter/Models/LoanPaidOffLetter.php

@@ -26,6 +26,7 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
  * @property string $loan_contract_date
  * @property string $loan_amount
  * @property string $loan_reason
+ * @property null|string $loan_file
  * @property \Illuminate\Support\Carbon $created_at
  * @property \Illuminate\Support\Carbon $updated_at
  */