Folder API: optionally force deleting Grafana 8 alerts when deleting a folder (or error) (#36427)

* Folder API: Add an optional query parameter for allowing deleting a  folder containing rules

* Update frontend

- Set forceDeleteRules=true when frontend deletes a folder
- Improve modal text

* Update docs

* Apply suggestions from code review

Co-authored-by: gotjosh <josue@grafana.com>
Co-authored-by: Nathan Rodman <nathanrodman@gmail.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

pkg/models/dashboards.go

@@ -363,8 +363,9 @@ type DashboardProvisioning struct {
 }
 
 type DeleteDashboardCommand struct {
-	Id    int64
-	OrgId int64
+	Id                     int64
+	OrgId                  int64
+	ForceDeleteFolderRules bool
 }
 
 type DeleteOrphanedProvisionedDashboardsCommand struct {

pkg/models/folders.go

@@ -15,6 +15,7 @@ var (
 	ErrFolderSameNameExists          = errors.New("a folder or dashboard in the general folder with the same name already exists")
 	ErrFolderFailedGenerateUniqueUid = errors.New("failed to generate unique folder ID")
 	ErrFolderAccessDenied            = errors.New("access denied to folder")
+	ErrFolderContainsAlertRules      = errors.New("folder contains alert rules")
 )
 
 type Folder struct {