Enhance the event store interface to support channeling (#7343)

- Avoids code duplication across the other targets. By having a
  centralized function call.

- Reduce the room for race.

pkg/event/targetlist_test.go

@@ -34,7 +34,12 @@ func (target ExampleTarget) ID() TargetID {
 	return target.id
 }
 
-func (target ExampleTarget) Send(eventData Event) error {
+// Save - Sends event directly without persisting.
+func (target ExampleTarget) Save(eventData Event) error {
+	return target.send(eventData)
+}
+
+func (target ExampleTarget) send(eventData Event) error {
 	b := make([]byte, 1)
 	if _, err := rand.Read(b); err != nil {
 		panic(err)
@@ -49,6 +54,11 @@ func (target ExampleTarget) Send(eventData Event) error {
 	return nil
 }
 
+// Send - interface compatible method does no-op.
+func (target ExampleTarget) Send(eventKey string) error {
+	return nil
+}
+
 func (target ExampleTarget) Close() error {
 	if target.closeErr {
 		return errors.New("close error")