Add Virtual Column _headers to URL Table Engine

Why it matters

This feature allows users to access and inspect HTTP response headers directly when querying the URL table engine, providing greater visibility and control over the metadata of HTTP requests. It solves the problem of not being able to see response headers natively, which is valuable for debugging, monitoring, and extracting metadata without additional HTTP client tools.

How to use it

When using the URL table engine, simply include the virtual column _headers in your SELECT statement to retrieve HTTP response headers alongside the requested data.