docs: add GCP IAP to external identity providers documentation

[msukkari]

Summary

This PR updates the external identity provider documentation to ensure all supported providers are documented and discoverable.

Changes

1. Added GCP IAP documentation - Google Cloud Identity-Aware Proxy was supported in the schema but missing from the documentation. Added comprehensive instructions including a note explaining how GCP IAP differs from other providers (infrastructure-level authentication via signed JWT headers).

2. Clarified Microsoft Entra ID / Azure AD - Updated the Microsoft Entra ID section to:

   • Add "(Azure AD)" to the header for discoverability
   • Added an info card explaining that Microsoft renamed Azure AD to Microsoft Entra ID in 2023, and that existing Azure AD setups will work with these instructions

Why

The issue reported that the external identity docs may be missing some supported providers (specifically mentioning "Microsoft AD"). After auditing:

• GCP IAP was the only provider supported in the schema but not documented
• Microsoft Entra ID (formerly Azure AD) was already documented, but users searching for "Azure AD" might not find it. Added clarification to improve discoverability.

Fixes SOU-777

Linear Issue: SOU-777

  

Summary by CodeRabbit

Documentation

• Enhanced Microsoft Entra ID documentation with clarification on the 2023 naming transition from Azure Active Directory
• Introduced new Google Cloud Identity-Aware Proxy (IAP) authentication configuration guide with setup instructions

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[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ef2f107c-0ba8-4395-bfe8-aab5234f4725

📥 Commits

Reviewing files that changed from the base of the PR and between 8af0a2c and c16fa93.

📒 Files selected for processing (1)

• docs/docs/configuration/idp.mdx

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Walkthrough

Documentation update to the IDP configuration guide renaming "Microsoft Entra ID" section and adding explanatory callouts for historical context. A new "Google Cloud IAP" section is introduced with setup instructions and configuration details for the gcp-iap provider.

Changes

Cohort / File(s)	Summary
IDP Documentation Updates docs/docs/configuration/idp.mdx	Renamed Microsoft Entra ID section with added Info callout explaining 2023 Microsoft rebranding; added new Google Cloud IAP section with explanation of non-OAuth flow, setup instructions, and configuration details (provider: "gcp-iap", purpose: "sso", audience.env).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Possibly related PRs

• Add support for GCP IAP JIT account provisioning #330: Documents the same GCP IAP SSO feature configuration with matching provider: "gcp-iap" and audience environment variable references.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch cursor/SOU-777-external-identity-documentation-adca

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[github-actions]

@msukkari your pull request is missing a changelog!