fix: Catch errors when failing to verify JWTs

[rolodato]

Fixes #4982.

The issue as described is incorrect, as the SAML routes already use AllowAny. The problem is actually caused by get_validated_token returning an exception when called with an invalid JWT. We now catch any of these expected errors and gracefully fail the authentication instead.

This is completely untested.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)			Feb 21, 2025 11:25pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)			Feb 21, 2025 11:25pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Feb 21, 2025 11:25pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-5153	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-5153	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-5153	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-5153	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-5153	Finished ✅	Results ✅

[github-actions]

Uffizzi Ephemeral Environment deployment-61216

☁️ https://app.uffizzi.com/github.com/Flagsmith/flagsmith/pull/5153

📄 View Application Logs etc.

What is Uffizzi? Learn more!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.47%. Comparing base (210519e) to head (6f8448e).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5153   +/-   ##
=======================================
  Coverage   97.46%   97.47%           
=======================================
  Files        1224     1224           
  Lines       42545    42571   +26     
=======================================
+ Hits        41466    41495   +29     
+ Misses       1079     1076    -3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[khvn26]

I am surprised that the new code path is covered by tests and no existing tests are modified, which suggests the backend behaviour is not changed by this PR?