feat: add update user endpoint

[emay2026]

This PR implements the PUT /users/:id endpoint to allow updating existing users.

Changes

• Added helper in for data mutation.
• Implemented in with:
  • Input validation requiring and (returns 400 on failure).
  • 404 response for non-existent user IDs.
  • 200 response with updated user object on success.
• Updated with implementation details and review findings.

Testing

Run

claude-course-starter@1.0.0 test
node --test

✔ NOTES.md exists at the project root (0.820417ms)
✔ NOTES.md has real content (0.436ms)
✔ PUT /users/:id updates an existing user (28.9385ms)
✔ PUT /users/:id returns 404 for a user that does not exist (2.637417ms)
✔ PUT /users/:id with a missing field returns 400 (2.539834ms)
✔ GET /health returns ok (16.754291ms)
✔ GET /users returns a list of users (4.866125ms)
✔ GET /users/:id returns 404 for a user that does not exist (3.02075ms)
✔ POST /users with no body returns 400 (6.367041ms)
ℹ tests 9
ℹ suites 0
ℹ pass 9
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 268.492458 to verify. Specifically, the following cases are covered:

• Updating an existing user (200 OK)
• Attempting to update a non-existent user (404 Not Found)
• Sending a request with missing fields (400 Bad Request)

[mateacademy-ai-mentor]

Review Summary

Your implementation fully meets all task requirements. The PUT /users/:id endpoint correctly handles all three success paths: it returns 400 when name or email are missing, 404 when the user doesn't exist, and 200 with the updated user on success. The code properly leverages the db/store.js updateUser helper and follows existing patterns throughout. All 9 tests pass, confirming no regressions. NOTES.md contains meaningful documentation covering your approach, model choice, and review findings. This is a solid implementation—you're clear to merge.

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