Creates requests with application/x-www-form-urlencoded body from
url.Values. Supports GetBody for retry compatibility, following the
same pattern as NewJSONRequest.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Implements the top-level httpx.Client that composes the full chain:
Logging → User Middlewares → Retry → Circuit Breaker → Balancer → Transport
- Response wrapper with JSON/XML/Bytes decoding and body caching
- NewJSONRequest helper with Content-Type and GetBody support
- Functional options: WithBaseURL, WithTimeout, WithRetry, WithEndpoints, etc.
- Integration tests covering retry, balancing, error mapping, and JSON round-trips
