Add pluggable Logon authentication for custom FIX signers

[0-jake-0]

Summary

Extends FIX adapter to support custom authentication schemes beyond simple passwords. Introduces FixLogon enum and LogonContext to allow venues like Binance to attach cryptographic signatures (e.g., Ed25519) bound to the exact Logon message bytes on the wire.

Key Changes

• New FixLogon enum with three variants:

  • None — no authentication fields (EncryptMethod/HeartBtInt/ResetSeqNumFlag only)
  • Password(String) — LMAX-style Username (tag 553) + Password (tag 554)
  • Custom(Arc<dyn Fn>) — caller-supplied builder for custom fields

• New LogonContext struct passed to custom builders, exposing:

  • msg_type, sender_comp_id, target_comp_id (header fields)
  • msg_seq_num, sending_time (exact values the Logon carries)
  • Enables signers to compute payloads over the canonical wire format

• Refactored message encoding:

  • SendingTime now formatted with millisecond precision (YYYYMMDD-HH:MM:SS.sss) to match venue requirements (e.g., Binance)
  • Extracted now_sending_time() helper to ensure consistent formatting
  • encode_message() takes sending_time parameter instead of computing it internally

• New send_with() method on FixSession:

  • Computes sequence number and SendingTime once
  • Passes both to a builder closure so signers see exactly what goes on the wire
  • Prevents timing skew between signature computation and wire encoding

• New public API:

  • fix_connect_tls_logon() — accepts FixLogon instead of Option<&str>
  • FixLogon::custom() — convenience constructor wrapping a builder in Arc
  • impl From<Option<&str>> for FixLogon — backward-compatible conversion

• Updated FixThreadedSource to store FixLogon instead of Option<String>

• Documentation in module-level comments and CLAUDE.md explaining the authentication flow and Binance Ed25519 example

Implementation Details

• FixLogon is Clone to allow capture in closures passed to the session loop
• Custom builders are Arc-wrapped to support Send + Sync across thread boundaries
• FixSession::send_logon() uses send_with() to ensure the builder receives the exact sequence number and formatted time the Logon will carry
• Backward compatibility maintained: fix_connect_tls(password: Option<&str>) now delegates to fix_connect_tls_logon() via FixLogon::from()
• Test added (custom_logon_fields_are_sent) verifying custom fields are encoded and accessible in the wire message

Notes

• Wingfoil remains venue/crypto-agnostic; Ed25519 implementation lives in the caller (e.g., the kes Binance adapter)
• Millisecond precision in SendingTime is required by Binance and is now the standard for all venues

https://claude.ai/code/session_01Q96qpjaqcpywW3rdy1eHjW

[0-jake-0]

Superseded by #418 (same commit; branch renamed to drop the venue name). Closing this one.

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