fix(transaction): correct optional field assignment and update tests

Replaced incorrect variable name in optional field assignment loop
(`optional` → `field_name`) to ensure only valid fields are set on
the request object. Updated unit tests to assert default CommandID and
Remarks behavior.

Author: RafaelJohn9

mpesakit/services/transaction.py

@@ -79,8 +79,8 @@ def query_status(
             "OriginalConversationID": original_conversation_id
         }
 
-        for optional, value in optionals.items():
-            if optional is not None:
-                setattr(request, optional, value)
+        for field_name, value in optionals.items():
+            if value is not None:
+                setattr(request, field_name, value)
 
         return self.transaction_status.query(request)

tests/unit/services/test_transaction_service.py

@@ -80,6 +80,7 @@ def test_query_status_default_command_id(transaction_service, mock_http_client):
         occasion="JuneSalary",
     )
 
+    assert resp.CommandID == "TransactionStatusQuery"
     assert isinstance(resp, TransactionStatusResponse)
     assert resp.is_successful() is True
     assert resp.ResponseDescription == "Accept the service request successfully."
@@ -107,6 +108,7 @@ def test_query_status_default_remarks(transaction_service, mock_http_client):
         occasion="JuneSalary",
     )
 
+    assert resp.Remarks == "Status Query"
     assert isinstance(resp, TransactionStatusResponse)
     assert resp.is_successful() is True
     assert resp.ResponseDescription == "Accept the service request successfully."