update links under the root README file

03-http-middleware/16-http-client-hygiene/README.md

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+# Kata 16: The HTTP Client Hygiene Wrapper
+**Target Idioms:** `net/http` Transport Reuse, Timeouts, Context-First APIs, Response Body Draining  
+**Difficulty:** 🔴 Advanced
+
+## 🧠 The "Why"
+“Works locally” HTTP code in Go often fails in prod because people:
+- use `http.DefaultClient` with no timeouts,
+- create a new client/transport per request (connection churn),
+- forget to close bodies (leaks + no keep-alive reuse),
+- don’t drain bodies (prevents connection reuse).
+
+This kata is about building a small internal SDK the **Go way**.
+
+## 🎯 The Scenario
+Your service calls a downstream API that sometimes returns large error bodies and sometimes hangs.
+You need:
+- strict timeouts,
+- proper cancellation,
+- safe connection reuse,
+- structured logs.
+
+## 🛠 The Challenge
+Implement:
+- `type APIClient struct { ... }`
+- `func (c *APIClient) GetJSON(ctx context.Context, url string, out any) error`
+
+### 1. Functional Requirements
+- [ ] Use `http.NewRequestWithContext`.
+- [ ] Decode JSON on 2xx responses into `out`.
+- [ ] On non-2xx: read up to N bytes of body and return an error including status code.
+
+### 2. The "Idiomatic" Constraints (Pass/Fail Criteria)
+- [ ] **Must NOT** use `http.DefaultClient`.
+- [ ] **Must** configure timeouts (`Client.Timeout` and/or transport-level timeouts).
+- [ ] **Must** reuse a single `Transport` (connection pooling).
+- [ ] **Must** `defer resp.Body.Close()`.
+- [ ] **Must** drain (at least partially) error bodies to allow connection reuse.
+- [ ] Use `slog` with fields: method, url, status, latency.
+
+## 🧪 Self-Correction (Test Yourself)
+- **If connections spike under load:** you probably rebuild transports.
+- **If keep-alives don’t work:** you likely didn’t drain/close body.
+- **If hangs occur:** you likely lack correct timeout configuration.
+
+## 📚 Resources
+- https://go.dev/src/net/http/client.go
+- https://go.dev/src/net/http/transport.go
+- https://blog.cloudflare.com/the-complete-guide-to-golang-net-http-timeouts/