feat: use the new logout endpoint (v4-apps)

[framitdavid]

Description

Switches the "Logg ut"-link in the app header from the legacy Altinn 2 endpoint to the new Altinn 3 platform endpoint.

• Before: https://{altinnHost}/ui/authentication/LogOut
• After: https://platform.{altinnHost}/authentication/api/v1/logout

Changes

• src/utils/urls/urlHelper.ts — logoutUrlAltinn(host) now builds the URL against the platform host (platform.<env>.altinn.<no|cloud>) and uses extractAltinnHost directly. Local-environment fallback (http://local.altinn.cloud[:port]/) and the undefined return for unknown hosts are unchanged.
• src/utils/urls/urlHelper.test.ts — Updated expected URLs for logoutUrlAltinn across prod / TT02 / AT21 / YT01.

The single callsite (src/components/presentation/AppHeader/AppHeaderMenu.tsx) is untouched — it consumes logoutUrlAltinn(window.location.host) and picks up the new URL automatically.

Resulting URLs per environment

Host the app runs on	Logout URL
*.apps.altinn.no (prod)	https://platform.altinn.no/authentication/api/v1/logout
*.apps.tt02.altinn.no (TT02)	https://platform.tt02.altinn.no/authentication/api/v1/logout
*.apps.at21.altinn.cloud (AT21)	https://platform.at21.altinn.cloud/authentication/api/v1/logout
*.apps.yt01.altinn.cloud (YT01)	https://platform.yt01.altinn.cloud/authentication/api/v1/logout
local.altinn.cloud[:port]	http://local.altinn.cloud[:port]/ (unchanged)
Unknown (studio etc.)	undefined (unchanged)

Related Issue(s)

• Closes the v4 part of following issue: Endring av endepunkt for logout i Altinn 3 altinn-studio#18676

Verification/QA

• Manual functionality testing
  • I have tested these changes manually
  • Creator of the original issue (or service owner) has been contacted for manual testing (or will be contacted when released in alpha)
  • No testing done/necessary
• Automated tests
  • Unit test(s) have been added/updated
  • Cypress E2E test(s) have been added/updated
  • No automatic tests are needed here (no functional changes/additions)
  • I want someone to help me make some tests
• UU/WCAG (follow these guidelines until we have our own)
  • I have tested with a screen reader/keyboard navigation/automated wcag validator
  • No testing done/necessary (no DOM/visual changes)
  • I want someone to help me perform accessibility testing
• User documentation @ altinn-studio-docs
  • Has been added/updated
  • No functionality has been changed/added, so no documentation is needed
  • I will do that later/have created an issue
• Support in Altinn Studio
  • Issue(s) created for support in Studio
  • This change/feature does not require any changes to Altinn Studio
• Sprint board
  • The original issue (or this PR itself) has been added to the Team Apps project and to the current sprint board
  • I don't have permissions to do that, please help me out
• Labels
  • I have added a kind/* and backport* label to this PR for proper release notes grouping
  • I don't have permissions to add labels, please help me out

Summary by CodeRabbit

• Bug Fixes
  • Updated logout endpoint configuration to use new authentication API endpoints across all environments (TT/AT/YT/Prod).

[coderabbitai]

📝 Walkthrough

Walkthrough

The logoutUrlAltinn() function is refactored to detect localhost using isLocalEnvironment() and construct logout endpoints via extractAltinnHost(), building URLs as https://platform.${altinnHost}/authentication/api/v1/logout instead of the legacy /ui/authentication/LogOut pattern. Tests are updated to match the new endpoint structure and hostnames.

Changes

Logout Endpoint Migration

Layer / File(s)	Summary
Core Implementation src/utils/urls/urlHelper.ts	logoutUrlAltinn() replaces host.match(localRegex) with isLocalEnvironment(host) for localhost detection, removes returnBaseUrlToAltinn() usage, and builds logout URLs as https://platform.${altinnHost}/authentication/api/v1/logout via extractAltinnHost().
Tests src/utils/urls/urlHelper.test.ts	Test assertions updated to expect /authentication/api/v1/logout endpoints under https://platform.<env>/ hostnames for TT, AT, YT, and Prod environments.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat: use the new logout endpoint (v4-apps)' clearly and concisely summarizes the main change: updating the logout endpoint implementation for v4 apps.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description is comprehensive and well-structured, following the template with clear technical details, a non-technical summary, related issue reference, and all verification/QA checkboxes appropriately addressed.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/use-the-new-logout-endpoint-a3

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud