Fix not-found pages issue (#12370)

[msynk]

closes #12370

Summary by CodeRabbit

• Bug Fixes
  • Improved HTTP error page handling to prevent response flushing errors across multiple server applications.

[coderabbitai]

Too many files changed? Review this PR in Change Stack to see how the pieces fit before you dive in.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 01bf5b73-384e-44df-9ab2-5ed0df9a476f

📥 Commits

Reviewing files that changed from the base of the PR and between ac60e3d and 300f8a3.

📒 Files selected for processing (4)

• src/BlazorUI/Demo/Bit.BlazorUI.Demo.Server/Startup/Middlewares.cs
• src/Websites/Careers/src/Bit.Websites.Careers.Server/Startup/Middlewares.cs
• src/Websites/Platform/src/Bit.Websites.Platform.Server/Startup/Middlewares.cs
• src/Websites/Sales/src/Bit.Websites.Sales.Server/Startup/Middlewares.cs

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Walkthrough

Four middleware files across BlazorUI Demo and website projects update HTTP error-page handling to defer status code assignment to Response.OnStarting callbacks. The pattern prevents exceptions during Blazor response rendering by avoiding immediate status code changes that could trigger body flushing.

Changes

HTTP Status Code Deferred Assignment

Layer / File(s)	Summary
BlazorUI Demo 401/403/404 Error Pages src/BlazorUI/Demo/Bit.BlazorUI.Demo.Server/Startup/Middlewares.cs	Routes containing "not-found" and "not-authorized" now defer status code setting via Response.OnStarting callbacks. For "not-authorized", the choice between 401 Unauthorized and 403 Forbidden is determined by the isForbidden query parameter. Comments clarify the interaction with Blazor rendering and UseStatusCodePages middleware.
Website 404 Error Pages src/Websites/Careers/src/Bit.Websites.Careers.Server/Startup/Middlewares.cs, src/Websites/Platform/src/Bit.Websites.Platform.Server/Startup/Middlewares.cs, src/Websites/Sales/src/Bit.Websites.Sales.Server/Startup/Middlewares.cs	Routes containing "not-found" now set 404 NotFound status code inside Response.OnStarting callbacks instead of direct assignment, consistent with the BlazorUI Demo pattern.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A hop, skip, and a deferred callback,
Status codes now wait their turn in the stack,
Before headers fly, the code finds its place,
No Blazor confusion—just grace upon grace!
The 404s and 401s align,
Delayed but not denied—a pattern divine! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main change - fixing the not-found pages issue with a reference to the related issue #12370, directly matching the PR's objective.
Linked Issues check	✅ Passed	The PR modifies middleware to defer HTTP status code assignment via OnStarting callbacks to prevent errors during response body handling, directly addressing the UnknownException issue reported in #12370.
Out of Scope Changes check	✅ Passed	All four modified middleware files address the same core issue of fixing not-found and unauthorized page handling, with no unrelated changes detected.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[Copilot]

Pull request overview

This PR addresses issue #12370 where navigating to /not-found on bitplatform.dev caused an exception instead of rendering the expected 404 UI, by deferring 404/401/403 status code assignment until the response is starting (so Blazor can render and flush the page body normally).

Changes:

• Defer setting the /not-found HTTP 404 status code via HttpResponse.OnStarting in the Sales, Platform, and Careers websites.
• Defer setting /not-found (404) and /not-authorized (401/403) status codes via OnStarting in the BlazorUI Demo server, with an added inline explanation of the underlying Blazor/StatusCodePages interaction.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/Websites/Sales/src/Bit.Websites.Sales.Server/Startup/Middlewares.cs	Defers /not-found status code to response start to avoid interfering with Blazor rendering / status-code handling.
src/Websites/Platform/src/Bit.Websites.Platform.Server/Startup/Middlewares.cs	Same deferred 404 approach for the Platform site (the site affected by #12370).
src/Websites/Careers/src/Bit.Websites.Careers.Server/Startup/Middlewares.cs	Aligns Careers site behavior by deferring the 404 status code for /not-found.
src/BlazorUI/Demo/Bit.BlazorUI.Demo.Server/Startup/Middlewares.cs	Defers 404/401/403 status codes for not-found/not-authorized pages and documents the rationale tied to enhanced navigation headers.