satellite/metabase: copy when source and destination are the same

If source and destination are the same, do nothing and return the original object.
Later, we will have to handle the case when metadata is changed, but for now it's not possible through libuplink.

An issue has been created for this (https://github.com/storj/storj/issues/5168)

Change-Id: I91cf48afeec498d3b2c219fa0d3baf2163cff384

satellite/metabase/copy_object.go

@@ -176,6 +176,10 @@ func (db *DB) FinishCopyObject(ctx context.Context, opts FinishCopyObject) (obje
 			return err
 		}
 
+		if objectAtDestination != nil && objectAtDestination.StreamID == sourceObject.StreamID {
+			newObject = sourceObject
+			return nil
+		}
 		if opts.VerifyLimits != nil {
 			err := opts.VerifyLimits(sourceObject.TotalEncryptedSize, int64(sourceObject.SegmentCount))
 			if err != nil {

satellite/metabase/copy_object_test.go

@@ -982,5 +982,34 @@ func TestFinishCopyObject(t *testing.T) {
 				}},
 			}.Check(ctx, t, db)
 		})
+
+		t.Run("finish copy object to same destination", func(t *testing.T) {
+			defer metabasetest.DeleteAll{}.Check(ctx, t, db)
+
+			obj := metabasetest.RandObjectStream()
+			numberOfSegments := 10
+			originalObj, _ := metabasetest.CreateTestObject{
+				CommitObject: &metabase.CommitObject{
+					ObjectStream:                  obj,
+					EncryptedMetadata:             testrand.Bytes(64),
+					EncryptedMetadataNonce:        testrand.Nonce().Bytes(),
+					EncryptedMetadataEncryptedKey: testrand.Bytes(265),
+				},
+			}.Run(ctx, t, db, obj, byte(numberOfSegments))
+
+			obj.StreamID = testrand.UUID()
+			_, expectedOriginalSegments, _ := metabasetest.CreateObjectCopy{
+				OriginalObject:   originalObj,
+				CopyObjectStream: &obj,
+			}.Run(ctx, t, db)
+
+			metabasetest.Verify{
+				Objects: []metabase.RawObject{
+					metabase.RawObject(originalObj),
+				},
+				Segments: expectedOriginalSegments,
+				Copies:   []metabase.RawCopy{},
+			}.Check(ctx, t, db)
+		})
 	})
 }