[reorg fix] [SCRS-2230] Configure source IP forwarding for GCP Service Extensions

[jhgilbert]

🤖 Auto-generated fix for #38779.

@eliottness — the docs repo reorg created merge conflicts in your PR #38779. This is an auto-generated replacement with the file paths fixed; please use it instead of the original.

This PR replays the commits from #38779 with file paths translated to the post-reorg hugo/ layout. The original commits are preserved — same messages and authorship.

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Original PR description:

What does this PR do? What is the motivation?

Fixes SCRS-2230

Updates the GCP Service Extensions Terraform deployment guide to configure forward_attributes = ["source.ip"] on google_network_services_lb_traffic_extension with provider = google-beta and update the required providers configuration to use google-beta. This ensures the service extension receives the client IP address observed by the load balancer for App and API Protection client-IP attribution.

Merge instructions

Merge readiness:

• Ready for merge

Additional notes

[datadog-official]

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