// Package httpx provides a high-level HTTP client with composable middleware
// for retry, circuit breaking, load balancing, structured logging, and more.
//
// The client is configured via functional options and assembled as a middleware
// chain around a standard http.RoundTripper:
//
//	Logging → User Middlewares → Retry → Circuit Breaker → Balancer → Transport
//
// # Quick start
//
//	client := httpx.New(
//	    httpx.WithBaseURL("https://api.example.com"),
//	    httpx.WithTimeout(10 * time.Second),
//	    httpx.WithRetry(),
//	    httpx.WithCircuitBreaker(),
//	)
//	defer client.Close()
//
//	resp, err := client.Get(ctx, "/users/1")
//
// # Request builders
//
// NewJSONRequest and NewFormRequest create requests with appropriate
// Content-Type headers and GetBody set for retry compatibility.
//
// # Error handling
//
// Failed requests return *httpx.Error with structured fields (Op, URL,
// StatusCode). Sentinel errors ErrRetryExhausted, ErrCircuitOpen, and
// ErrNoHealthy can be checked with errors.Is.
//
// # Sub-packages
//
//   - middleware — client-side middleware (logging, auth, headers, recovery, request ID)
//   - retry — configurable retry with backoff and Retry-After support
//   - circuitbreaker — per-host circuit breaker (closed → open → half-open)
//   - balancer — client-side load balancing with health checking
//   - server — production HTTP server with router, middleware, and graceful shutdown
package httpx