Sticky wire-exchange trace id derived from message content

[ar]

Implements #769.

What

One trace id per wire exchange, derived from message content so request and response share it with no carrier on the wire and regardless of protocol version.

ISOMsg

• naturalTraceId(): first two MTI digits plus the trace-id fields present (default 3, 7, 11, 12, 41, 42, trimmed; 37 and 32 are excluded because a server often mints them, 7 and 12 keep a wrapped STAN from linking to old exchanges), hashed to a 32-hex UUID. null when none of the key fields is present. setTraceIdFields(int...) tunes the field list system-wide.
• setTraceId(String) / getClaimedTraceId(): an explicitly asserted id. Transient, copied by clone, never packed.
• getTraceId(): the effective id. Natural when computable, else the claim, else a random id minted once and kept as the claim.

BaseChannel send and receive events: trace-id = the message's effective id; new session tag = socket UUID (which used to be the trace id); trace-claimed = the claimed id, only when it differs from the effective one.

IncomingListener puts ContextConstants.TRACE_ID (new) into the Context.

TransactionManager uses the Context trace id for the transaction event, falling back to the per-transaction id when absent.

SendResponse claims the Context trace id on the response when it has no claim of its own, so a response whose key fields changed still links back through trace-claimed.

Not changed

No wire field. No thread-locals. LogEvent trace-id format stays 32 hex. Session events in ISOServer are unchanged.

Behaviour notes

• A retransmission (0201) shares the original's id: the MTI class and key fields are the same. That is the same wire exchange for correlation purposes.
• A MUX-originated request from a participant gets its own natural id; linking it to the inbound transaction's id is a follow-up (claim from the Context in QueryHost).
• CMF DE-113.22 adopt/echo is a follow-up once a DE-113 subfield packager exists.

Tests

• ISOMsgTest: request/response share the natural id, a different STAN differs, claim copied by clone and never overrides the natural id, a message without key fields gets a stable minted id.
• IncomingListenerTest (new): the queued Context carries the message's id.
• ISOServerTest.testChannelEventsCarryTheExchangeTraceIdAndSessionTag (new): a real client-to-server exchange; the client's send event and the server's receive event carry the same trace-id, both carry session, neither carries trace-claimed.
• Full :jpos:test and :jpos:javadoc pass.

Release note

Channel send / receive events: trace-id now identifies the wire exchange rather than the connection; the connection id moved to the session tag. Consumers that joined channel events on trace-id per connection should use session.