Add Python OBO flow frontend and backend sample

[TarunReddy-msft]

Description

This PR adds a Python-based sample demonstrating the On-Behalf-Of (OBO) authentication
flow using a simple frontend and backend structure. The sample is intended to help
developers understand how to structure OBO-enabled Copilot integrations in Python.

Changes

• Added python/samples/backend.py - OBO token acquisition and backend logic
• Added python/samples/frontend.py - frontend interaction layer
• Added python/samples/README.md - OBO flow documentation
• Retained original python/README.md without changes

Purpose

Provide a minimal, easy-to-understand reference implementation for implementing
OBO authentication flows in Python for Microsoft 365 Copilot scenarios.

Testing

• Verified locally using a valid Azure App Registration
• Confirmed token acquisition and request flow works as expected
• No secrets or tenant-specific values are committed

Notes

This change is additive and does not modify or impact existing samples or packages.

[TarunReddy-msft]

@microsoft-github-policy-service agree

[gavinbarron]

@TarunReddy-msft Thanks for contributing these samples.

Can we please use a folder structure like this to organize and keep things tidy

└── python
  └── samples
   ├── backend.py
   └── backend.py

[TarunReddy-msft]

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