Add comprehensive HTTP header support based on IANA registry
- Add ~45 new standard headers to header_name.ml organized by RFC/category
(CORS, security, WebSocket, authentication, digest headers)
- Add header category lists and predicates for header classification
- Create header_parsing.ml/mli with RFC 9110 header value parsing:
- Content-Range parsing for partial content (206 responses)
- If-Range parsing (ETag vs Last-Modified detection)
- Allow header method list parsing
- Authentication-Info parsing for Digest auth nextnonce
- Retry-After and Accept-Ranges parsing
- Create websocket.ml/mli with RFC 6455 handshake support:
- Sec-WebSocket-Key generation (16 random bytes, base64)
- Sec-WebSocket-Accept computation/validation (SHA-1 + GUID)
- Protocol and extension negotiation
- Upgrade headers helper and response validation
- Add IANA HTTP fields registry CSV to specs folder for reference
- Add comprehensive test suites (50 tests total):
- test_header_parsing.ml: 24 tests
- test_websocket.ml: 26 tests
- Export new modules from requests.ml/mli
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>