[Anshuu2004]

What does this PR do?

The join endpoint's 400 for a missing code or username was the only error in http-server that did not go through the shared errorResponse helper. It sent { message: "..." } instead of { success: false, error: "..." }. JoinQuiz.tsx reads response.data.error, so for that response it always fell back to the generic "Failed to join quiz" and the real message was dropped.

I changed that one line in sessionController.ts to errorResponse(res, 400, "Code and username are required"), and added a small test file for joinQuizController so the shape is pinned down.

I did not touch the frontend. JoinQuiz.tsx already reads .error, so it works with the new shape as is.

Related issue

Closes #192

Type of change

• Bug fix
• New feature
• Documentation
• Refactoring
• Performance
• Tests
• Build / CI / deployment

Which services does this touch?

• apps/frontend
• apps/http-server
• apps/ws-server
• apps/genAI
• packages/db (schema or Prisma changes)
• Docker / CI

How did you test this?

I grepped all of apps/http-server/src for res.status(...).json(...) and res.sendStatus. The only error path that was not using errorResponse was the one on sessionController.ts line 29. Everything else raw is a success response (200/201), so I left those alone.

I added apps/http-server/src/controllers/sessionController.test.ts, written the same way as authController.test.ts (mocked @repo/db, fake req/res). It checks that an empty body, a missing username, a missing code and an empty username all give a 400 with { success: false, error: "Code and username are required" } and never touch the database. There is also one check that the 404 for an unknown quiz has the same shape.

Commands, run in apps/http-server on a fresh worktree of upstream/main:

pnpm test        # before: 7 files, 75 tests passed
pnpm test        # after:  8 files, 80 tests passed
pnpm check-types # no errors (after running db:generate in packages/db)

I also put the old res.status(400).json({ message }) line back temporarily with the new test in place and the 4 new 400 tests failed, so the test does catch the bug. Then I restored the fix.

I did not run the whole app with docker compose, and I did not open the join screen in a browser. For the frontend I only read JoinQuiz.tsx to confirm it reads data.error. This repo's http-server has no lint script, so I did not run pnpm run lint or pnpm run build.

Checklist

• I ran pnpm run lint
• I ran pnpm check-types in apps/http-server (not the root turbo run)
• I ran pnpm run build
• The app still starts with docker-compose up
• I updated documentation if this changes behaviour or setup
• I did not commit any .env file, API key or other secret