Python: Add Purview Middleware

[Rishabh4275]

Motivation and Context

Description

Adds Python Purview Middleware which adds Purview policy evaluation to the Microsoft Agent Framework. It lets you enforce data security / governance policies on both the prompt (user input + conversation history) and the model response before they proceed further in your workflow.
All changes are additive—no breaking changes to existing packages.

Follow-Up Opportunities

1. Add caching for protection scope computations.
2. Introduce higher-level policy decision aggregation object.
3. Background Processing for flows that do not lead to a response, so shortcircuit
4. Retry/backoff for 429 responses with telemetry counters.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull Request Overview

This PR adds Microsoft Purview integration to the Python Agent Framework, enabling data security and governance policy evaluation on conversational AI content. The implementation provides middleware that can block prompts or responses based on centrally managed Purview policies.

Key changes:

• Complete Purview middleware integration with authentication, API clients, and content processing capabilities
• Comprehensive model system using Pydantic for Microsoft Graph API interactions and policy evaluation
• Full test coverage with extensive unit tests for all components and integration scenarios

Reviewed Changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
python/samples/getting_started/purview_agent/	Sample application demonstrating Purview middleware usage with Azure OpenAI
python/packages/purview/tests/	Comprehensive test suite covering all middleware components and edge cases
python/packages/purview/pyproject.toml	Package configuration with dependencies and development tools
python/packages/purview/agent_framework_purview/	Core implementation including models, client, processor, middleware, and settings
python/packages/purview/README.md	Documentation with usage examples and configuration guidance
python/packages/purview/LICENSE	MIT license for the package

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[eavanvalkenburg]

I'm no expert on the back and forth to and from Purview, so I haven't looked deeply at that. Overall I think the structure can be simplified, in python we tend to prefer less files even if they are longer, also the models folder is a concern, because even though it appears empty (because of the empty all) it will still be indexed by our api docs tooling. So please fix that. I also wonder about Agent vs ChatMiddleware for this, but it could even be both...

[Rishabh4275]

@microsoft-github-policy-service agree company="Microsoft"

@microsoft-github-policy-service agree company="Microsoft"

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/core/agent_framework/azure
_shared.py	79	7	91%	135–136, 199, 202, 215, 217, 227
TOTAL	10378	1664	83%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1352	98 💤	0 ❌	0 🔥	27.945s ⏱️

[Rishabh4275]

@eavanvalkenburg Could you have a look.
Thank you.