The WrapUDPConn constructor returns nil when either arg is nil, so
c.stats is always non-nil in all udpConn methods. Remove 8 redundant
nil guards that were inconsistent with packetConn (which already
skipped them).
Add 65 unit tests across plugin, stats, and wrapper packages covering
nil safety, race conditions, double-close, event marshaling, and
reset-traffic semantics. Replace magic numbers in tests with named
Kind constants.
- WrapUDPConn, WrapPacketConn, WrapListener: add nil guards for pc/ln params
- NewGRPCPlugin: return no-op observer instead of nil on connection error
- gRPC plugin: fix resource leak by wiring Close() through observerWrapper
and service.Close() lifecycle
- Both plugins: log unknown event types instead of silently dropping them
- httpPlugin: remove dead nil check for always-non-nil client field
- Stats.Reset: update core interface doc to match implementation behavior
- Add doc comments to all exported symbols across the observer package
ginuerzh