Python: Add dependencies param to ag-ui FastAPI endpoint

[moonbox3]

Motivation and Context

• Add dependencies parameter to add_agent_framework_fastapi_endpoint() for middleware-like behavior
• Update getting_started server example to demonstrate usage pattern
• Add documentation for the new parameter

Description

Improve usage of FastAPI endpoint for AG-UI library.

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.

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/ag-ui/agent_framework_ag_ui
_endpoint.py	44	0	100%
TOTAL	17648	2878	83%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
2630	155 💤	0 ❌	0 🔥	1m 2s ⏱️

[Copilot]

Pull request overview

This PR adds a dependencies parameter to the add_agent_framework_fastapi_endpoint() function to enable authentication and authorization for AG-UI endpoints using FastAPI's dependency injection system. The changes include comprehensive test coverage, updated documentation, and a working example demonstrating API key authentication.

Changes:

• Added dependencies parameter to FastAPI endpoint creation function for middleware-like authentication/authorization
• Updated getting_started server example with complete API key authentication implementation
• Added comprehensive documentation in README with authentication examples and best practices

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
python/packages/ag-ui/agent_framework_ag_ui/_endpoint.py	Added dependencies parameter to endpoint function signature and passed it to FastAPI decorator
python/packages/ag-ui/tests/test_endpoint.py	Added 4 new tests covering unauthorized blocking, authorized access, multiple dependencies, and backward compatibility
python/packages/ag-ui/getting_started/server.py	Added comprehensive authentication example with API key verification and security best practices documentation
python/packages/ag-ui/README.md	Added detailed security section with authentication examples and integration options