feat(gateway): Update pdk functions for sandbox

[Icarus9913]

Description

Docs about updating pdk functions for sandbox, to be releases with Kong 3.15.

Refer to

• https://github.com/Kong/kong-ee/pull/18223
• https://github.com/Kong/kong-ee/pull/18227

Preview Links

Checklist

• Tested how-to docs. If not, note why here.
• All pages contain metadata.
• Any new docs link to existing docs.
• All autogenerated instructions render correctly (API, decK, Konnect, Kong Manager).
• Style guide (capitalized gateway entities, placeholder URLs) implemented correctly.
• Every page has a description entry in frontmatter.
• Add new pages to the product documentation index (if applicable).

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[netlify]

✅ Deploy Preview for kongdeveloper ready!

Name	Link
🔨 Latest commit	0a46c7e
🔍 Latest deploy log	https://app.netlify.com/projects/kongdeveloper/deploys/6a0d565b7a20ec0008f6394e
😎 Deploy Preview	https://deploy-preview-5298--kongdeveloper.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
🤖 Make changes	Run an agent on this branch

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[Copilot]

Pull request overview

Updates the Gateway Lua sandboxing reference to reflect additional PDK functions that are available in sandboxed environments (intended for Kong Gateway 3.15).

Changes:

• Added kong.client.get_identity_realm_source / kong.client.set_identity_realm_source to the strict-mode allowlist.
• Added a strict-mode “Kong Router PDK” section (kong.router.get_route, kong.router.get_service) and removed the redundant lax-mode listing.
• Added kong.request.get_id, kong.request.get_raw_forwarded_path, and kong.table.new to the strict-mode allowlist.