Dashboards: Fix creating dashboard under folder using deprecated API (#77501)

* Dashboards: Add integration tests for creating a dashboard

* Fix creating dashboard under folder using deprecated API

* Update swagger response

* Fix comments

pkg/services/folder/folderimpl/folder.go

@@ -116,7 +116,7 @@ func (s *Service) Get(ctx context.Context, cmd *folder.GetFolderQuery) (*folder.
 	var dashFolder *folder.Folder
 	var err error
 	switch {
-	case cmd.UID != nil:
+	case cmd.UID != nil && *cmd.UID != "":
 		dashFolder, err = s.getFolderByUID(ctx, cmd.OrgID, *cmd.UID)
 		if err != nil {
 			return nil, err

pkg/services/folder/service.go

@@ -13,9 +13,9 @@ type Service interface {
 	Create(ctx context.Context, cmd *CreateFolderCommand) (*Folder, error)
 
 	// GetFolder takes a GetFolderCommand and returns a folder matching the
-	// request. One of ID, UID, or Title must be included. If multiple values
+	// request. One of UID, ID or Title must be included. If multiple values
 	// are included in the request, Grafana will select one in order of
-	// specificity (ID, UID, Title).
+	// specificity (UID, ID, Title).
 	Get(ctx context.Context, cmd *GetFolderQuery) (*Folder, error)
 
 	// Update is used to update a folder's UID, Title and Description. To change