PatchUserRequest now uses Patch<T> for the five removable fields
(user_ad_tag, max_tcp_conns, expiration_rfc3339, data_quota_bytes,
max_unique_ips). Sending JSON null drops the entry from the
corresponding access HashMap; sending 0 is preserved as a literal
limit; omitted fields stay untouched. The handler synchronises the
in-memory ip_tracker on both set and remove of max_unique_ips. A
helper parse_patch_expiration mirrors parse_optional_expiration for
the new three-state field. Runtime semantics are unchanged.
- Enhanced linting rules in `src/proxy/mod.rs` to enforce stricter code quality checks in production.
- Updated hash functions in `src/proxy/middle_relay.rs` for better efficiency.
- Added new security tests in `src/proxy/tests/middle_relay_stub_completion_security_tests.rs` to validate desynchronization behavior.
- Removed ignored test stubs in `src/proxy/tests/middle_relay_security_tests.rs` to clean up the test suite.
- Improved error handling and code readability in various transport modules, including `src/transport/middle_proxy/config_updater.rs` and `src/transport/middle_proxy/pool.rs`.
- Introduced new padding functions in `src/stream/frame_stream_padding_security_tests.rs` to ensure consistent behavior across different implementations.
- Adjusted TLS stream validation in `src/stream/tls_stream.rs` for better boundary checking.
- General code cleanup and dead code elimination across multiple files to enhance maintainability.
