Add comprehensive documentation generation tools and scripts

- Introduced DOCUMENTATION_TOOLS.md to compare various C# documentation generation tools, including DocFX, xmldocmd, and others.
- Created api/index.md for Weaviate C# Client API documentation overview and key namespaces.
- Configured docfx.json for DocFX documentation generation.
- Added scripts for generating HTML and Markdown documentation, including generate-docs-html.sh, generate-docs-html.ps1, generate-docs-markdown.py, and their respective PowerShell and Bash scripts.
- Implemented xmldocmd scripts for Markdown documentation generation, including generate-docs-xmldocmd.sh and generate-docs-xmldocmd.ps1.
- Updated README files in scripts directory to provide usage instructions and prerequisites for documentation generation.

Author: mpartipilo

DOCUMENTATION.md

@@ -0,0 +1,399 @@
+# API Documentation Guide
+
+This document explains how to generate and maintain API documentation for the Weaviate C# Client.
+
+## Overview
+
+The Weaviate C# Client uses XMLDoc comments in the source code to generate API documentation in two formats:
+- **HTML** - Professional, searchable documentation website using DocFX
+- **Markdown** - Simple, portable markdown files
+
+## Quick Start
+
+### Generate HTML Documentation
+
+```bash
+# macOS/Linux
+./scripts/generate-docs-html.sh
+
+# Windows
+.\scripts\generate-docs-html.ps1
+```
+
+Output: `_site/` directory
+View: `docfx serve _site` then open http://localhost:8080
+
+### Generate Markdown Documentation
+
+```bash
+# macOS/Linux
+./scripts/generate-docs-markdown.sh
+
+# Direct Python call
+python3 scripts/generate-docs-markdown.py src/Weaviate.Client/bin/Release/net9.0/Weaviate.Client.xml docs/api-markdown
+```
+
+Output: `docs/api-markdown/` directory
+View: `docs/api-markdown/index.md`
+
+## Documentation Status
+
+### Current Coverage
+
+As of this implementation:
+- **Total public types:** 384
+- **Documented types:** ~36% (including recently added documentation)
+- **XML generation:** Enabled in project file
+
+### Recently Documented (High Priority)
+
+✅ **Model Classes:**
+- `Vector`, `VectorSingle<T>`, `VectorMulti<T>` - Vector data types
+- `Vectors` - Vector collection
+- `Filter`, `PropertyFilter`, `ReferenceFilter` - Filtering system
+- `Sort` - Sort specifications
+- `BatchInsertRequest`, `BatchInsertResponse` - Batch operations
+
+✅ **Infrastructure:**
+- XML documentation file generation enabled in `Weaviate.Client.csproj`
+- DocFX configuration (`docfx.json`)
+- Documentation generation scripts
+
+### To Be Documented
+
+The following high-priority areas still need XMLDoc comments:
+
+**Configuration Classes:**
+- `VectorConfig`, `VectorConfigList`
+- `InvertedIndexConfig`
+- `ShardingConfig`
+- `ReplicationConfig`
+- `MultiTenancyConfig`
+- `BM25Config`, `StopwordConfig`
+
+**Model Classes:**
+- `Property`, `Reference` - Collection schema
+- `Collection`, `CollectionConfig` - Collection configuration
+- `VectorIndex.*` - HNSW, Flat, Dynamic configurations
+- `Vectorizer.*` - All vectorizer variants
+- RBAC models in `Rbac.cs`
+
+**Serialization:**
+- `IPropertyConverter`, `PropertyConverterBase`
+- `PropertyBag`, `PropertyConverterRegistry`
+- Individual property converters
+
+## Project Configuration
+
+### XML Documentation Settings
+
+Location: `src/Weaviate.Client/Weaviate.Client.csproj`
+
+```xml
+<PropertyGroup>
+  <!-- Enable XML documentation generation -->
+  <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  <DocumentationFile>bin\$(Configuration)\$(TargetFramework)\Weaviate.Client.xml</DocumentationFile>
+  <!-- Suppress warnings for missing XML comments (remove this line once all public APIs are documented) -->
+  <NoWarn>$(NoWarn);CS1591</NoWarn>
+</PropertyGroup>
+```
+
+**Note:** The `CS1591` warning suppression should be removed once all public APIs are documented.
+
+## Writing XMLDoc Comments
+
+### Basic Structure
+
+```csharp
+/// <summary>
+/// Brief description of the type or member.
+/// </summary>
+/// <remarks>
+/// Detailed explanation, usage notes, or important information.
+/// Can include multiple paragraphs.
+/// </remarks>
+/// <param name="paramName">Description of the parameter.</param>
+/// <returns>Description of the return value.</returns>
+/// <exception cref="ExceptionType">When this exception is thrown.</exception>
+/// <example>
+/// <code>
+/// var example = new MyClass();
+/// example.DoSomething();
+/// </code>
+/// </example>
+public class MyClass
+{
+    // Implementation
+}
+```
+
+### Key Tags
+
+- `<summary>` - Brief description (required for all public APIs)
+- `<remarks>` - Additional details, usage notes
+- `<param>` - Parameter descriptions
+- `<typeparam>` - Generic type parameter descriptions
+- `<returns>` - Return value description
+- `<exception>` - Exceptions that may be thrown
+- `<example>` - Code examples
+- `<code>` - Code blocks within examples
+- `<see cref=""/>` - Cross-reference to other types/members
+- `<seealso cref=""/>` - Related types/members
+
+### Best Practices
+
+1. **Be Concise** - Summaries should be one or two sentences
+2. **Be Specific** - Describe what the member does, not how it works
+3. **Include Examples** - Especially for complex APIs
+4. **Cross-Reference** - Use `<see cref=""/>` to link related types
+5. **Document Parameters** - Explain purpose, valid values, constraints
+6. **Document Returns** - Describe what is returned and when
+7. **Note Exceptions** - Document all exceptions that can be thrown
+
+### Example from Vector.cs
+
+```csharp
+/// <summary>
+/// Represents a vector for use with Weaviate, supporting both single and multi-vector configurations.
+/// Vectors can contain numeric values of various types (double, float, int, etc.) and can be implicitly converted from native arrays.
+/// </summary>
+/// <remarks>
+/// This is the base class for all vector types in the Weaviate client library.
+/// Use <see cref="VectorSingle{T}"/> for single vectors or <see cref="VectorMulti{T}"/> for multi-vector representations.
+/// Supports implicit conversion from and to native C# arrays.
+/// </remarks>
+public abstract record Vector : IEnumerable, IHybridVectorInput
+{
+    /// <summary>
+    /// Gets or initializes the name of this vector. Defaults to "default".
+    /// Used to identify specific vectors in multi-vector configurations.
+    /// </summary>
+    public string Name { get; init; } = "default";
+}
+```
+
+## Documentation Generation Scripts
+
+### HTML Generation (DocFX)
+
+**Files:**
+- `scripts/generate-docs-html.sh` - Bash script for macOS/Linux
+- `scripts/generate-docs-html.ps1` - PowerShell script for Windows
+- `docfx.json` - DocFX configuration
+- `api/index.md` - API documentation landing page
+
+**Prerequisites:**
+```bash
+# Install DocFX
+dotnet tool install -g docfx
+```
+
+**Process:**
+1. Builds the project in Release configuration
+2. Generates XML documentation file
+3. Runs `docfx metadata` to extract API information
+4. Runs `docfx build` to generate HTML site
+
+**Output:** `_site/` directory containing complete HTML documentation
+
+### Markdown Generation (Python)
+
+**Files:**
+- `scripts/generate-docs-markdown.py` - Python script (cross-platform)
+- `scripts/generate-docs-markdown.sh` - Bash wrapper script
+
+**Prerequisites:**
+- Python 3.x (usually pre-installed on macOS/Linux)
+
+**Process:**
+1. Builds the project in Release configuration
+2. Parses the generated XML documentation file
+3. Generates individual markdown files for each type
+4. Creates an index file organized by namespace
+
+**Output:** `docs/api-markdown/` directory with markdown files
+
+## Viewing Documentation
+
+### HTML Documentation
+
+**Local Preview:**
+```bash
+docfx serve _site
+# Open http://localhost:8080
+```
+
+**Features:**
+- Full-text search
+- Namespace/type navigation tree
+- Cross-references between types
+- Dark/light theme
+- Responsive design
+
+### Markdown Documentation
+
+**View Locally:**
+- Open `docs/api-markdown/index.md` in any markdown viewer
+- Use VSCode, Typora, or GitHub's markdown preview
+- Or use tools like `grip`: `grip docs/api-markdown/index.md`
+
+**Features:**
+- Simple, portable format
+- Easy to read and version control
+- Compatible with GitHub, GitLab, etc.
+
+## Publishing Documentation
+
+### GitHub Pages
+
+1. Generate HTML documentation:
+   ```bash
+   ./scripts/generate-docs-html.sh
+   ```
+
+2. Push to `gh-pages` branch:
+   ```bash
+   git add _site -f
+   git subtree push --prefix _site origin gh-pages
+   ```
+
+3. Enable GitHub Pages in repository settings pointing to `gh-pages` branch
+
+### CI/CD Integration
+
+**GitHub Actions Example:**
+
+```yaml
+name: Generate Documentation
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Install DocFX
+        run: dotnet tool install -g docfx
+
+      - name: Generate Documentation
+        run: ./scripts/generate-docs-html.sh
+
+      - name: Deploy to GitHub Pages
+        if: github.ref == 'refs/heads/main'
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_site
+```
+
+## Maintenance
+
+### Adding Documentation to New Code
+
+When adding new public APIs:
+
+1. **Write XMLDoc comments** following the patterns in this guide
+2. **Build and check warnings** to ensure proper formatting:
+   ```bash
+   dotnet build --configuration Release
+   ```
+3. **Test documentation generation** to verify output:
+   ```bash
+   ./scripts/generate-docs-markdown.sh
+   ```
+
+### Updating Existing Documentation
+
+1. Edit XMLDoc comments in source files
+2. Rebuild the project
+3. Regenerate documentation
+4. Review changes in generated files
+
+### Removing CS1591 Warning Suppression
+
+Once all public APIs are documented:
+
+1. Remove `<NoWarn>$(NoWarn);CS1591</NoWarn>` from `Weaviate.Client.csproj`
+2. Build and fix any remaining warnings about missing documentation
+3. Enable this as a CI check to enforce documentation on new code
+
+## Troubleshooting
+
+### XML File Not Generated
+
+**Problem:** Documentation scripts report missing XML file
+
+**Solution:**
+1. Ensure `GenerateDocumentationFile` is `true` in project file
+2. Build in Release configuration: `dotnet build --configuration Release`
+3. Check for build errors
+
+### DocFX Not Found
+
+**Problem:** `docfx: command not found`
+
+**Solution:**
+```bash
+dotnet tool install -g docfx
+# Or update: dotnet tool update -g docfx
+```
+
+### Python Not Found
+
+**Problem:** `python3: command not found` (Windows)
+
+**Solution:**
+- Download and install Python from [python.org](https://www.python.org/downloads/)
+- Ensure "Add Python to PATH" is checked during installation
+
+### Warnings About Missing Documentation
+
+**Problem:** CS1591 warnings during build
+
+**Status:** Expected - these indicate undocumented public APIs
+
+**Solution:**
+- Add XMLDoc comments to the reported types/members
+- Or keep `CS1591` suppressed in `NoWarn` (current configuration)
+
+## Resources
+
+### Documentation Tools
+
+- **DocFX:** https://dotnet.github.io/docfx/
+- **XMLDoc Guide:** https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/xmldoc/
+- **Markdown Guide:** https://www.markdownguide.org/
+
+### Example Documentation
+
+See these files for well-documented examples:
+- `src/Weaviate.Client/Models/VectorData.cs` - Vector types
+- `src/Weaviate.Client/Models/Filter.cs` - Filter API
+- `src/Weaviate.Client/Models/Sort.cs` - Sort API
+- `src/Weaviate.Client/Models/Batch.cs` - Batch operations
+
+## Contributing
+
+When contributing documentation:
+
+1. Follow the patterns established in existing documentation
+2. Include examples for complex APIs
+3. Cross-reference related types using `<see cref=""/>`
+4. Test documentation generation before submitting PR
+5. Ensure all new public APIs have XMLDoc comments
+
+---
+
+For questions or issues related to documentation, please file an issue on the GitHub repository.