Item and buyer ledger implementation

[kmate129]

Introduces the implementation of Buyer Ledger and Item Ledger classes and integrates them into the existing template. In accordance with the xsd, I dynamically defined both ledgers and their fields as optional, deviating from the previous template description.

[theriverman]

What makes this inline dict declaration necessary compared to adding the actual XML template between an IF-block? For example, it could look something like this:

        {% if buyer.buyer_ledger %}
        <vevoFokonyv>
            <konyvelesDatum>{{ buyer.buyer_ledger.accounting_date }}</konyvelesDatum>
            <vevoAzonosito>{{ buyer.buyer_ledger.buyer_identifier }}</vevoAzonosito>
            <vevoFokonyviSzam>{{ buyer.buyer_ledger.buyer_ledger_number }}</vevoFokonyviSzam>
            <folyamatosTelj>{{ buyer.buyer_ledger.continuous_performance }}</folyamatosTelj>
            <elszDatumTol>{{ buyer.buyer_ledger.settlement_date_from }}</elszDatumTol>
            <elszDatumIg>{{ buyer.buyer_ledger.settlement_date_to }}</elszDatumIg>
        </vevoFokonyv>
        {% endif %}

If buyer.buyer_ledger is true, we're safe to add the whole block to the request and this block can be added only once and the keys would never change dynamically to my knowledge, hence I don't see why compiling them on-the-fly is needed. According to the XSD scheme I don't really see a scenario when one of the <vevoFokonyvTipus> elements would be not needed but even then the field could be left empty (szamlazz.hu ignores empty fields I believe) or we can just put between IF-blocks as well.

If I'm overseeing something or there's some extra logic making this reasonable then I'm of course fine with the solution but could you please give me an explanation to better understand what's happening?

Thanks!

[theriverman]

Thanks for the PR, @kmate129 !
I've have a couple of questions about your implementation before merging it. Please see my inline comments in the PR.

[kmate129]

Thank you for the review. I have refactored my solution for both BuyerLedger and ItemLedger to use IF conditions. In terms of readability, it is indeed better than the dynamic approach.

The settlement_date_from and settlement_date_to fields are of type date and optional. I need to bind their rendering to an IF condition because, in the model I followed the schema for field types, treating them as strings. As a result, if left empty, a validation error occurs because an empty string does not match the date type required by xsd. Similarly, this applies to BuyerLedger.accounting_date.

For BuyerLedger.continuous_performance, if buyer.buyer_ledger is not set (None), the template engine will still try to access the continuous_performance field. However, since there is no BuyerLedger instance, the template engine generates an empty string. It also violates the xsd, handled by IF clause.