Send kafka notification messages in batches when queue_dir is enabled (#18164)

Fixes #18124

internal/event/targetlist.go

@@ -22,6 +22,8 @@ import (
 	"strings"
 	"sync"
 	"sync/atomic"
+
+	"github.com/minio/minio/internal/store"
 )
 
 const (
@@ -34,7 +36,7 @@ type Target interface {
 	ID() TargetID
 	IsActive() (bool, error)
 	Save(Event) error
-	SendFromStore(string) error
+	SendFromStore(store.Key) error
 	Close() error
 	Store() TargetStore
 }