refactor(examples): extract writeJSON helper in HTTP handlers

[appleboy]

Summary

Extracts a small local writeJSON helper in the three Go HTTP examples
(go-jwks, go-jwks-multi, go-webservice) to replace the Content-Type header +
json.NewEncoder(...).Encode(...) boilerplate that was repeated 3–4× per file.
Centralizes JSON response writing so the content-type header can't drift between
handlers. Pure refactor — no behavior change.

AI Authorship

• AI was used. Details:
  • Tool / model: Claude Opus 4.8 via Claude Code (/simplify)
  • AI-authored files: go-jwks/main.go, go-jwks-multi/main.go, go-webservice/main.go
  • Human line-by-line reviewed: ⚠️ None yet — author has not reviewed the diff line-by-line. Reviewer should read all three files closely.

Change classification

• Leaf node (local impact) — standalone teaching example apps; nothing depends on them.
• Core code

Plan reference

No plan — originated from a /simplify cleanup pass over the codebase. The consensus finding across the reuse/altitude/simplification review angles was the repeated JSON-response boilerplate.

Verification

• Unit tests — N/A (these example apps ship no tests by repo convention)
• Integration tests — N/A
• e2e tests — N/A
• Stress / soak test — N/A
• Performed: go build ./... and go vet ./... pass cleanly in all three modules.
• Manual verification for reviewer: run any example (e.g. cd go-jwks && go run main.go) and confirm /health and the /api/* endpoints still return Content-Type: application/json with the same JSON bodies as before.

Verifiability check

• Inputs and outputs are documented — diff is mechanical; response shapes unchanged.
• Reviewer can judge correctness without reading every line — writeJSON is a 3-line helper; each call site is a 1:1 substitution.
• Failures will surface in monitoring — N/A (examples).

Risk & rollback

• Risk: Very low. Only risk is a missed call site or a changed response shape; both are visible in the diff and caught by go vet/build.
• Rollback: git revert 63d1bc1 — single self-contained commit.

Reviewer guide

• Read carefully: the three writeJSON definitions are identical; confirm each handler's substitution preserved its exact map payload and that no handler lost its content-type header.
• Spot-check OK: the main() / startup code in each file is untouched.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR refactors JSON response writing in the Go HTTP examples by extracting a shared local writeJSON helper in each file, reducing repeated response boilerplate without changing response payloads.

Changes:

• Replaced repeated Content-Type and json.NewEncoder(...).Encode(...) blocks with writeJSON.
• Updated health handlers to use the same helper.
• Added identical local writeJSON helpers to the three affected examples.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
go-webservice/main.go	Uses writeJSON for profile, data, and health JSON responses.
go-jwks/main.go	Uses writeJSON for protected endpoint and health JSON responses.
go-jwks-multi/main.go	Uses writeJSON for multi-issuer endpoint and health JSON responses.

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