fix financial issues

tests/app/Models/PaymentModelMetadataTest.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Tests\App\Models;
+
+use App\Models\PaymentModel;
+use CodeIgniter\Test\CIUnitTestCase;
+
+class PaymentModelMetadataTest extends CIUnitTestCase
+{
+    public function testAllowedFieldsIncludeInstallmentSequence(): void
+    {
+        $model = new PaymentModel();
+        $fields = self::getPrivateProperty($model, 'allowedFields');
+
+        $this->assertContains('installment_seq', $fields);
+        $this->assertContains('transaction_id', $fields);
+        $this->assertContains('check_file', $fields);
+    }
+}