[Feature] Minimal IUCLID export (#338)

This is an initial implementation that creates a working minimal .i6z document.
It passes schema validation and can be imported into IUCLID.

Caveat:
IUCLID files target individual compounds.
Pathway is not actually covered by the format.

It can be added in either soil or water and soil OECD endpoints.
**I currently only implemented the soil endpoint for all data.**

This sort of works, and I can report all degradation products in a pathway (not a nice view, but we can report many transformation products and add a diagram attachment in the future).

Adding additional information is an absolute pain, as we need to explicitly map each type of information to the relevant OECD field.
I use the XSD scheme for validation, but unfortunately the IUCLID parser is not fully compliant and requires a specific order, etc.

The workflow is: finding the AI structure from the XSD scheme -> make the scheme validation pass -> upload to IUCLID to get obscure error messages -> guess what could be wrong -> repeat 💣

New specifications get released once per year, so we will have to update accordingly.
I believe that this should be a more expensive feature, as it requires significant effort to uphold.

Currently implemented for root compound only in SOIL:

- Soil Texture 2
- Soil Texture 1
- pH value
- Half-life per soil sample / scenario (mapped to disappearance; not sure about that).
- CEC
- Organic Matter (only Carbon)
- Moisture content
- Humidity

<img width="2123" alt="image.png" src="attachments/d29830e1-65ef-4136-8939-1825e0959c62">
<img width="2124" alt="image.png" src="attachments/ac9de2ac-bf68-4ba4-b40b-82f810a9de93">
<img width="2139" alt="image.png" src="attachments/5674c7e6-865e-420e-974a-6b825b331e6c">

Reviewed-on: enviPath/enviPy#338
Co-authored-by: Tobias O <tobias.olenyi@envipath.com>
Co-committed-by: Tobias O <tobias.olenyi@envipath.com>

epiuclid/builders/base.py

@@ -0,0 +1,105 @@
+import xml.etree.ElementTree as ET
+from datetime import datetime, timezone
+
+# IUCLID 6 XML namespaces
+NS_PLATFORM_CONTAINER = "http://iuclid6.echa.europa.eu/namespaces/platform-container/v2"
+NS_PLATFORM_METADATA = "http://iuclid6.echa.europa.eu/namespaces/platform-metadata/v1"
+NS_PLATFORM_FIELDS = "http://iuclid6.echa.europa.eu/namespaces/platform-fields/v1"
+NS_XLINK = "http://www.w3.org/1999/xlink"
+
+# Register namespace prefixes for clean output
+ET.register_namespace("i6c", NS_PLATFORM_CONTAINER)
+ET.register_namespace("i6m", NS_PLATFORM_METADATA)
+ET.register_namespace("i6", NS_PLATFORM_FIELDS)
+ET.register_namespace("xlink", NS_XLINK)
+
+IUCLID_VERSION = "6.0.0"
+DEFINITION_VERSION = "10.0"
+CREATION_TOOL = "enviPath"
+
+
+def _tag(ns: str, local: str) -> str:
+    return f"{{{ns}}}{local}"
+
+
+def _sub(parent: ET.Element, ns: str, local: str, text: str | None = None) -> ET.Element:
+    """Create a sub-element under parent. Only sets text if not None."""
+    elem = ET.SubElement(parent, _tag(ns, local))
+    if text is not None:
+        elem.text = str(text)
+    return elem
+
+
+def _sub_if(parent: ET.Element, ns: str, local: str, text: str | None = None) -> ET.Element | None:
+    """Create a sub-element only when text is not None."""
+    if text is None:
+        return None
+    return _sub(parent, ns, local, text)
+
+
+def build_platform_metadata(
+    document_key: str,
+    document_type: str,
+    name: str,
+    document_sub_type: str | None = None,
+    parent_document_key: str | None = None,
+    order_in_section_no: int | None = None,
+) -> ET.Element:
+    """Build the <i6c:PlatformMetadata> element for an i6d document."""
+    pm = ET.Element(_tag(NS_PLATFORM_CONTAINER, "PlatformMetadata"))
+
+    now = datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ")
+
+    _sub(pm, NS_PLATFORM_METADATA, "iuclidVersion", IUCLID_VERSION)
+    _sub(pm, NS_PLATFORM_METADATA, "documentKey", document_key)
+    _sub(pm, NS_PLATFORM_METADATA, "documentType", document_type)
+    _sub(pm, NS_PLATFORM_METADATA, "definitionVersion", DEFINITION_VERSION)
+    _sub(pm, NS_PLATFORM_METADATA, "creationDate", now)
+    _sub(pm, NS_PLATFORM_METADATA, "lastModificationDate", now)
+    _sub(pm, NS_PLATFORM_METADATA, "name", name)
+    if document_sub_type:
+        _sub(pm, NS_PLATFORM_METADATA, "documentSubType", document_sub_type)
+    if parent_document_key:
+        _sub(pm, NS_PLATFORM_METADATA, "parentDocumentKey", parent_document_key)
+    if order_in_section_no is not None:
+        _sub(pm, NS_PLATFORM_METADATA, "orderInSectionNo", str(order_in_section_no))
+    _sub(pm, NS_PLATFORM_METADATA, "i5Origin", "false")
+    _sub(pm, NS_PLATFORM_METADATA, "creationTool", CREATION_TOOL)
+
+    return pm
+
+
+def build_document(
+    document_key: str,
+    document_type: str,
+    name: str,
+    content_element: ET.Element,
+    document_sub_type: str | None = None,
+    parent_document_key: str | None = None,
+    order_in_section_no: int | None = None,
+) -> str:
+    """Build a complete i6d document XML string."""
+    root = ET.Element(_tag(NS_PLATFORM_CONTAINER, "Document"))
+
+    pm = build_platform_metadata(
+        document_key=document_key,
+        document_type=document_type,
+        name=name,
+        document_sub_type=document_sub_type,
+        parent_document_key=parent_document_key,
+        order_in_section_no=order_in_section_no,
+    )
+    root.append(pm)
+
+    content_wrapper = _sub(root, NS_PLATFORM_CONTAINER, "Content")
+    content_wrapper.append(content_element)
+
+    _sub(root, NS_PLATFORM_CONTAINER, "Attachments")
+    _sub(root, NS_PLATFORM_CONTAINER, "ModificationHistory")
+
+    return ET.tostring(root, encoding="unicode", xml_declaration=True)
+
+
+def document_key(uuid) -> str:
+    """Format a UUID as an IUCLID document key (uuid/0 for raw data)."""
+    return f"{uuid}/0"