API: Support creating a nested folder (#58508)

* API: Support nested folder creation

* Update swagger

* fixup

* Update pkg/api/dtos/folder.go

Co-authored-by: Serge Zaitsev <serge.zaitsev@grafana.com>

* Fix some tests

* create legacy folder url from title and uid

Co-authored-by: idafurjes <36131195+idafurjes@users.noreply.github.com>
Co-authored-by: Serge Zaitsev <serge.zaitsev@grafana.com>
Co-authored-by: Ida Furjesova <ida.furjesova@grafana.com>

pkg/api/dtos/folder.go

@@ -22,6 +22,8 @@ type Folder struct {
 	Updated       time.Time              `json:"updated"`
 	Version       int                    `json:"version"`
 	AccessControl accesscontrol.Metadata `json:"accessControl,omitempty"`
+	// only used if nested folders are enabled
+	ParentUID string `json:"parentUid"`
 }
 
 type FolderSearchHit struct {