Add mandatory PATCH_PDFWRITER.md documentation

Complete mandatory documentation for PyPDF2 compatibility.
This package benefits from oca-ocb-base compatibility layer.

🤖 assisted by claude

odoo-bringout-oca-edi-pdf_helper/doc/PATCH_PDFWRITER.md

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+# PyPDF2 Compatibility Patch - PDF Helper (EDI)
+
+## Overview
+
+This package benefits from the PyPDF2 compatibility fixes implemented in the `oca-ocb-base` package. The pdf_helper module uses `OdooPdfFileWriter` and `OdooPdfFileReader` classes that are automatically compatible with PyPDF2 3.0.0+ through the main compatibility layer.
+
+## Problem
+
+In PyPDF2 3.0.0, several classes and methods were deprecated and removed:
+- `PdfFileWriter` → `PdfWriter`
+- `PdfFileReader` → `PdfReader`
+- Various method names changed (e.g., `addPage()` → `add_page()`)
+
+## Affected Functionality
+
+The pdf_helper module uses PyPDF2 indirectly through:
+- `OdooPdfFileWriter` for embedding XML attachments in PDFs
+- `OdooPdfFileReader` for extracting XML files from PDF documents
+- XML-to-PDF embedding for EDI workflows
+- PDF parsing and attachment processing
+
+## Solution
+
+**This package requires NO direct patches** because it uses:
+1. `OdooPdfFileWriter` from `odoo.tools.pdf` (oca-ocb-base)
+2. `OdooPdfFileReader` from `odoo.tools.pdf` (oca-ocb-base)
+
+The main compatibility layer in `oca-ocb-base` handles all PyPDF2 version compatibility automatically.
+
+## Files Using PyPDF2
+
+### `pdf_helper/utils.py`
+- Imports `PdfReadError` with compatibility handling
+- Uses `OdooPdfFileReader` (automatically compatible)
+
+### `pdf_helper/models/helper.py`  
+- Uses `OdooPdfFileWriter` and `OdooPdfFileReader` (automatically compatible)
+- Calls methods like `cloneReaderDocumentRoot()` and `addAttachment()`
+
+## Implementation Details
+
+**No code changes needed** in this package. Compatibility is achieved through:
+
+1. **Dependency**: Requires `oca-ocb-base` with `pdfwrite` branch
+2. **Automatic compatibility**: `OdooPdfFileWriter`/`OdooPdfFileReader` handle all PyPDF2 version differences
+3. **Import handling**: Exception imports handle both old and new PyPDF2 locations
+
+## Testing
+
+The compatibility has been verified with:
+- PyPDF2 3.0.0+ (new API)
+- PyPDF2 2.x (old API)
+- XML embedding in PDFs
+- XML extraction from PDFs
+- EDI document processing workflows
+
+## Branch Information
+
+- **Branch**: `pdfwrite`
+- **Based on**: Current master branch
+- **Type**: Dependency compatibility (no direct patches)
+- **Impact**: Automatic compatibility through oca-ocb-base dependency
+
+## Dependencies
+
+**CRITICAL**: This package requires:
+- `oca-ocb-base` package on `pdfwrite` branch
+- The main PyPDF2 compatibility layer must be active
+
+## Author
+
+- **Developer**: Ernad Husremović (hernad@bring.out.ba)
+- **Company**: bring.out.doo Sarajevo
+- **Date**: 2025-09-02
+
+## Related Issues
+
+This documentation addresses PyPDF2 compatibility for:
+- EDI XML embedding workflows
+- PDF attachment processing
+- Electronic document interchange
+
+## Installation
+
+1. Ensure `oca-ocb-base` is using the `pdfwrite` branch
+2. Use this package's `pdfwrite` branch (for documentation compliance)
+3. No additional installation steps required
+
+## Future Considerations
+
+- Monitor oca-ocb-base compatibility updates
+- Test EDI workflows with future PyPDF2 versions
+- Consider direct PyPDF2 usage optimization if needed