Enhance relay testing and event handling

- Updated TestRelay to include a wait mechanism for relay readiness, improving test reliability.
- Refactored startTestRelay to return the assigned port, allowing dynamic port assignment.
- Added timestamp validation in HandleEvent to reject events with timestamps more than one hour in the future.
- Introduced channels for handling OK and COUNT messages in the Client struct, improving message processing.
- Updated tests to reflect changes in event timestamp handling and increased wait times for event processing.
- Bumped version to v0.20.6 to reflect these enhancements.

app/handle-event.go

@@ -176,6 +176,18 @@ func (l *Listener) HandleEvent(msg []byte) (err error) {
 		}
 		return
 	}
+	// validate timestamp - reject events too far in the future (more than 1 hour)
+	now := time.Now().Unix()
+	if env.E.CreatedAt > now+3600 {
+		if err = Ok.Invalid(
+			l, env,
+			"timestamp too far in the future",
+		); chk.E(err) {
+			return
+		}
+		return
+	}
+
 	// verify the signature
 	var ok bool
 	if ok, err = env.Verify(); chk.T(err) {