Add SendAuthErrorEvent, SendConnectEvent, SendDisconnectEvent to
InternalEventSystem, plus AuthErrorEventCount counter and the three
companion detail record types (AuthErrorDetail, ConnectEventDetail,
DisconnectEventDetail). 10 new tests in AuthErrorEventTests all pass.
Add RemoteServerShutdownEvent, RemoteServerUpdateEvent, LeafNodeConnectEvent,
and LeafNodeDisconnectEvent types plus matching EventSubjects constants, with
10 unit tests covering type identity, field assignment, format placeholders,
and JSON roundtrip serialization.
Add EventBuilder static class to EventTypes.cs with helpers for constructing
fully-populated ConnectEventMsg, DisconnectEventMsg, AccountNumConns, and
ServerStatsMsg. Also add RemoteServerShutdownEvent, RemoteServerUpdateEvent,
LeafNodeConnectEvent, and LeafNodeDisconnectEvent advisory types.
Add FullEventPayloadTests.cs (10 tests) covering all builders, GenerateEventId
uniqueness, GetTimestamp ISO 8601 format, DataStats zero defaults, and
ConnectEventMsg JSON roundtrip.