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/target/elasticsearch.go

@@ -69,8 +69,13 @@ func (target *ElasticsearchTarget) ID() event.TargetID {
 	return target.id
 }
 
-// Send - sends event to Elasticsearch.
-func (target *ElasticsearchTarget) Send(eventData event.Event) error {
+// Save - Sends event directly without persisting.
+func (target *ElasticsearchTarget) Save(eventData event.Event) error {
+	return target.send(eventData)
+}
+
+func (target *ElasticsearchTarget) send(eventData event.Event) error {
+
 	var key string
 
 	remove := func() error {
@@ -111,6 +116,11 @@ func (target *ElasticsearchTarget) Send(eventData event.Event) error {
 	return nil
 }
 
+// Send - interface compatible method does no-op.
+func (target *ElasticsearchTarget) Send(eventKey string) error {
+	return nil
+}
+
 // Close - does nothing and available for interface compatibility.
 func (target *ElasticsearchTarget) Close() error {
 	return nil