Feat: Stream Videos from UC Volumes into a Databricks App using FastAPI

[ImaneTS]

Description

Adds documentation for streaming video files from Unity Catalog volumes in FastAPI applications.

Motivation

Multiple customers have been working on video streaming use cases from UC volumes but are struggling without proper code examples. This PR provides a complete, production-ready code snippet that demonstrates how to:

• Authenticate using OAuth 2.0 client credentials flow
• Stream video files from Unity Catalog volumes using the Databricks Files API
• Support range requests for video seeking and progressive loading
• Handle chunked streaming for efficient memory usage
• Validate responses to catch authentication issues early

Changes

• Added new documentation page: docs/docs/fastapi/building_endpoints/volumes_stream_video.mdx
• Included complete code snippet with OAuth token generation and video streaming endpoint
• Documented required environment variables, permissions, and dependencies
• Followed existing FastAPI documentation format and style

Testing

Documentation follows the established pattern from other FastAPI endpoint examples in the cookbook.

Related Resources

• Databricks Files API
• Unity Catalog Volumes