Nested folders: Fix move (#65526)

* Nested Folders: Fix move response

Fix JSON tags to be consistent with the GET endpoint

* Add API test for moving to root folder

* Allow move to root folder

* Fix failure message

* Update OpenAPI specification

pkg/services/folder/folderimpl/sqlstore_test.go

@@ -390,9 +390,10 @@ func TestIntegrationGetParents(t *testing.T) {
 		require.NoError(t, err)
 	})
 
-	t.Run("get parents of unknown folder should return an error", func(t *testing.T) {
-		_, err := folderStore.GetParents(context.Background(), folder.GetParentsQuery{})
-		require.ErrorIs(t, err, folder.ErrFolderNotFound)
+	t.Run("get parents of root folder should should be empty", func(t *testing.T) {
+		parents, err := folderStore.GetParents(context.Background(), folder.GetParentsQuery{})
+		require.NoError(t, err)
+		require.Empty(t, parents)
 	})
 
 	t.Run("get parents of 1-st level folder should be empty", func(t *testing.T) {