fix: net_amount calculation

[blaggacao]

depends on:

• feat: get_meta can derive meta from dict frappe#28525
• fix: meta signature frappe#28526

This PR ensures that item_tax_rate is populated from the doc-wide template, if available and if no item wise tax has been set.

This is necessary to match net_amounts to account heads in taxes and totals.

fixes: #44219

---

Before NOK

❯ tail -f erpnext.controllers.taxes_and_totals.log
2024-11-20 00:10:43,131 DEBUG erpnext.controllers.taxes_and_totals Sales Invoice (FUP00006) ...
2024-11-20 00:10:43,132 DEBUG erpnext.controllers.taxes_and_totals  Item 0: ALMBOT1050
2024-11-20 00:10:43,132 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 50420.17             tax_amount: 9579.83              - IVA @ 19
2024-11-20 00:10:43,132 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 50420.17             tax_amount: 0.0                  - 240805 - IVA Descontable
2024-11-20 00:10:43,132 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 50420.17             tax_amount: 26.82                - Gastos de personal (fijo)
2024-11-20 00:10:43,132 DEBUG erpnext.controllers.taxes_and_totals  Item 1: ARAN500 - {'240801 - IVA Generado - P': 0.0, '240805 - IVA Descontable - P': 0.0}
2024-11-20 00:10:43,133 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 0.0                  - IVA @ 19
2024-11-20 00:10:43,133 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 0.0                  - 240805 - IVA Descontable
2024-11-20 00:10:43,134 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 53.18                - Gastos de personal (fijo)

Now OK
compare net_amount of ALMBOT1050 for 240805 - IVA Descontable and also note the new item rate {'240801 - IVA Generado - P': 19.0} addition

❯ tail -f erpnext.controllers.taxes_and_totals.log
2024-11-20 02:48:38,133 DEBUG erpnext.controllers.taxes_and_totals Sales Invoice (FUP00006) ...
2024-11-20 02:48:38,135 DEBUG erpnext.controllers.taxes_and_totals  Item 0: ALMBOT1050 - {'240801 - IVA Generado - P': 19.0}
2024-11-20 02:48:38,135 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 50420.17             tax_amount: 9579.83              - IVA @ 19
2024-11-20 02:48:38,136 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 0.0                  tax_amount: 0.0                  - 240805 - IVA Descontable
2024-11-20 02:48:38,136 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 50420.17             tax_amount: 26.82                - Gastos de personal (fijo)
2024-11-20 02:48:38,136 DEBUG erpnext.controllers.taxes_and_totals  Item 1: ARAN500 - {'240801 - IVA Generado - P': 0.0, '240805 - IVA Descontable - P': 0.0}
2024-11-20 02:48:38,137 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 0.0                  - IVA @ 19
2024-11-20 02:48:38,137 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 0.0                  - 240805 - IVA Descontable
2024-11-20 02:48:38,138 DEBUG erpnext.controllers.taxes_and_totals   net_amount: 100000.0             tax_amount: 53.18                - Gastos de personal (fijo)