event: Set contentType as well under NotificationEvent. (#4003)

This is an enhancement change to to cater support all
the data fields present on the object. Currently
we only send a subset of data which object info
provides us.

It also helps us keep a full namespace mirror on
notification targets for efficient query.

cmd/bucket-notification-datatypes.go

@@ -139,6 +139,8 @@ type objectMeta struct {
 	Key         string            `json:"key"`
 	Size        int64             `json:"size,omitempty"`
 	ETag        string            `json:"eTag,omitempty"`
+	ContentType string            `json:"contentType:omitempty"`
+	UserDefined map[string]string `json:"userDefined:omitempty"`
 	VersionID   string            `json:"versionId,omitempty"`
 	Sequencer   string            `json:"sequencer"`
 }

cmd/event-notifier.go

@@ -156,6 +156,7 @@ func newNotificationEvent(event eventData) NotificationEvent {
 	if event.Type == ObjectRemovedDelete {
 		nEvent.S3.Object = objectMeta{
 			Key:       escapedObj,
+			VersionID: "1",
 			Sequencer: uniqueID,
 		}
 		return nEvent
@@ -166,6 +167,9 @@ func newNotificationEvent(event eventData) NotificationEvent {
 		Key:         escapedObj,
 		ETag:        event.ObjInfo.MD5Sum,
 		Size:        event.ObjInfo.Size,
+		ContentType: event.ObjInfo.ContentType,
+		UserDefined: event.ObjInfo.UserDefined,
+		VersionID:   "1",
 		Sequencer:   uniqueID,
 	}