feat(validation): Implement EN16931 compliance validation types and VAT categories

- Added validation types for EN16931 compliance in `validation.types.ts`, including interfaces for `ValidationResult`, `ValidationOptions`, and `ValidationReport`.
- Introduced `VATCategoriesValidator` in `vat-categories.validator.ts` to validate VAT categories according to EN16931 rules, including detailed checks for standard, zero-rated, exempt, reverse charge, intra-community, export, and out-of-scope services.
- Enhanced `IEInvoiceMetadata` interface in `en16931-metadata.ts` to include additional fields required for full standards compliance, such as delivery information, payment information, allowances, and charges.
- Implemented helper methods for VAT calculations and validation logic to ensure accurate compliance with EN16931 standards.

assets/schematron/EN16931-CII-v1.3.14.meta.json

@@ -0,0 +1,7 @@
+{
+  "source": "EN16931-CII",
+  "version": "1.3.14",
+  "url": "https://github.com/ConnectingEurope/eInvoicing-EN16931/raw/master/cii/schematron/EN16931-CII-validation.sch",
+  "format": "CII",
+  "downloadDate": "2025-08-11T11:05:40.209Z"
+}

assets/schematron/EN16931-CII-v1.3.14.sch

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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Licensed under European Union Public Licence (EUPL) version 1.2.
+
+-->
+<!-- 
+
+        	CII syntax binding to the TC434   
+ -->
+<schema xmlns="http://purl.oclc.org/dsdl/schematron"
+  xmlns:rsm="urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100"
+  xmlns:ccts="urn:un:unece:uncefact:documentation:standard:CoreComponentsTechnicalSpecification:2"
+  xmlns:udt="urn:un:unece:uncefact:data:standard:UnqualifiedDataType:100"
+  xmlns:qdt="urn:un:unece:uncefact:data:standard:QualifiedDataType:100"
+  xmlns:ram="urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:100"
+  queryBinding="xslt2">
+  <title>EN16931 model bound to CII</title>
+  <ns prefix="rsm"  uri="urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100"/>
+  <ns prefix="ccts" uri="urn:un:unece:uncefact:documentation:standard:CoreComponentsTechnicalSpecification:2"/>
+  <ns prefix="udt"  uri="urn:un:unece:uncefact:data:standard:UnqualifiedDataType:100"/>
+  <ns prefix="qdt"  uri="urn:un:unece:uncefact:data:standard:QualifiedDataType:100"/>
+  <ns prefix="ram"  uri="urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:100"/>
+  <ns prefix="xs"   uri="http://www.w3.org/2001/XMLSchema"/>
+  <phase id="EN16931-model-phase">
+    <active pattern="EN16931-CII-Model"/>
+  </phase>
+  <phase id="codelist_phase">
+    <active pattern="EN16931-Codes"/>
+  </phase>
+  <phase id="syntax_phase">
+    <active pattern="EN16931-CII-Syntax"/>
+  </phase>
+  <!-- Abstract CEN BII patterns -->
+  <!-- ========================= -->
+  <include href="abstract/EN16931-CII-model.sch"/>
+  <include href="abstract/EN16931-CII-syntax.sch"/>
+  <!-- Data Binding parameters -->
+  <!-- ======================= -->
+  <include href="CII/EN16931-CII-model.sch"/>
+  <include href="CII/EN16931-CII-syntax.sch"/>
+  <!-- Code Lists Binding rules -->
+  <!-- ======================== -->
+  <include href="codelist/EN16931-CII-codes.sch"/>
+</schema>

assets/schematron/EN16931-EDIFACT-v1.3.14.meta.json

@@ -0,0 +1,7 @@
+{
+  "source": "EN16931-EDIFACT",
+  "version": "1.3.14",
+  "url": "https://github.com/ConnectingEurope/eInvoicing-EN16931/raw/master/edifact/schematron/EN16931-EDIFACT-validation.sch",
+  "format": "CII",
+  "downloadDate": "2025-08-11T11:05:40.547Z"
+}

assets/schematron/EN16931-EDIFACT-v1.3.14.sch

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Licensed under European Union Public Licence (EUPL) version 1.2.
+
+-->
+<!-- 
+
+        	EDIFACT syntax binding to the EN16931   
+        	Author: Andreas Pelekies
+          Timestamp: 2016-10-31 00:00:00 +0200
+ -->
+<schema xmlns="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2">
+  <title>EN16931 model bound to EDIFACT</title>  
+  <phase id="EN16931-model-phase">
+    <active pattern="EN16931-EDIFACT-Model"/>
+  </phase>
+  <phase id="codelist_phase">
+    <active pattern="EN16931-Codes"/>
+  </phase>
+  <phase id="syntax_phase">
+    <active pattern="EN16931-EDIFACT-Syntax"/>
+  </phase>
+  <!-- Abstract CEN BII patterns -->
+  <!-- ========================= -->
+  <include href="abstract/EN16931-EDIFACT-model.sch"/>
+  <include href="abstract/EN16931-EDIFACT-syntax.sch"/>
+  <!-- Data Binding parameters -->
+  <!-- ======================= -->
+  <include href="EDIFACT/EN16931-EDIFACT-model.sch"/>
+  <include href="EDIFACT/EN16931-EDIFACT-syntax.sch"/>
+  <!-- Code Lists Binding rules -->
+  <!-- ======================== -->
+  <include href="codelist/EN16931-EDIFACT-codes.sch"/>
+</schema>

assets/schematron/EN16931-UBL-v1.3.14.meta.json

@@ -0,0 +1,7 @@
+{
+  "source": "EN16931-UBL",
+  "version": "1.3.14",
+  "url": "https://github.com/ConnectingEurope/eInvoicing-EN16931/raw/master/ubl/schematron/EN16931-UBL-validation.sch",
+  "format": "UBL",
+  "downloadDate": "2025-08-11T11:05:39.868Z"
+}

assets/schematron/EN16931-UBL-v1.3.14.sch

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Licensed under European Union Public Licence (EUPL) version 1.2.
+
+-->
+<schema xmlns="http://purl.oclc.org/dsdl/schematron" xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2" xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2" xmlns:cn="urn:oasis:names:specification:ubl:schema:xsd:CreditNote-2" xmlns:UBL="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2" queryBinding="xslt2">
+  <title>EN16931  model bound to UBL</title>
+  <ns prefix="ext" uri="urn:oasis:names:specification:ubl:schema:xsd:CommonExtensionComponents-2"/>
+  <ns prefix="cbc" uri="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2"/>
+  <ns prefix="cac" uri="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2"/>
+  <ns prefix="qdt" uri="urn:oasis:names:specification:ubl:schema:xsd:QualifiedDataTypes-2"/>
+  <ns prefix="udt" uri="urn:oasis:names:specification:ubl:schema:xsd:UnqualifiedDataTypes-2"/>
+  <ns prefix="cn"  uri="urn:oasis:names:specification:ubl:schema:xsd:CreditNote-2"/>
+  <ns prefix="ubl" uri="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"/>
+  <ns prefix="xs"  uri="http://www.w3.org/2001/XMLSchema"/>
+  <phase id="EN16931model_phase">
+    <active pattern="UBL-model"/>
+  </phase>
+  <phase id="codelist_phase">
+    <active pattern="Codesmodel"/>
+  </phase>
+  <!-- Abstract CEN BII patterns -->
+  <!-- ========================= -->
+  <include href="abstract/EN16931-model.sch"/>
+  <include href="abstract/EN16931-syntax.sch"/>
+  <!-- Data Binding parameters -->
+  <!-- ======================= -->
+  <include href="UBL/EN16931-UBL-model.sch"/>
+  <include href="UBL/EN16931-UBL-syntax.sch"/>
+  <!-- Code Lists Binding rules -->
+  <!-- ======================== -->
+  <include href="codelist/EN16931-UBL-codes.sch"/>
+</schema>

assets/schematron/PEPPOL-EN16931-UBL-v3.0.17.meta.json

@@ -0,0 +1,7 @@
+{
+  "source": "PEPPOL-EN16931-UBL",
+  "version": "3.0.17",
+  "url": "https://github.com/OpenPEPPOL/peppol-bis-invoice-3/raw/master/rules/sch/PEPPOL-EN16931-UBL.sch",
+  "format": "UBL",
+  "downloadDate": "2025-08-11T11:05:40.954Z"
+}