feat: add HTTP request/response body logging with RequestLogger trait

[ammario]

Summary

• Implement comprehensive HTTP request/response body logging functionality
• Add RequestLogger trait for cleaner, more extensible architecture
• Support streaming body logging with zero performance impact when disabled

Key Changes

New Architecture

• RequestLogger trait: Clean abstraction with FileRequestLogger and NoopLogger implementations
• Cleaner API: RuleEngine now accepts Arc instead of Option<Arc<Mutex>>

Body Logging Features

• Environment-controlled: Enabled via HTTPJAIL_REQUEST_LOG_BODY environment variable
• Streaming implementation: Bodies logged as they stream through, avoiding memory overhead
• Request correlation: 4-character hex IDs correlate request/response pairs
• Binary data handling: Automatic base64 encoding for non-UTF8 data
• Truncation: Large bodies truncated at 10KB with clear indication

Log Format

2024-01-15T10:23:45.123Z --> 3e4f + GET https://api.example.com/users
2024-01-15T10:23:45.124Z --> 3e4f:REQ {"user": "alice"}
2024-01-15T10:23:45.234Z <-- 3e4f 200 OK
2024-01-15T10:23:45.235Z <-- 3e4f:BODY {"id": 123, "name": "Alice"}

Test Plan

• All existing tests pass
• New integration tests for body logging functionality
• Tests for NoopLogger behavior
• Tests for request ID generation and uniqueness
• Tests for both allowed and denied requests

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