Access control: FGAC for annotation updates (#46462)

* proposal

* PR feedback

* fix canSave bug

* update scope naming

* linting

* linting

Co-authored-by: Ezequiel Victorero <ezequiel.victorero@grafana.com>

pkg/services/annotations/annotations.go

@@ -145,3 +145,17 @@ type ItemDTO struct {
 	AvatarUrl   string           `json:"avatarUrl"`
 	Data        *simplejson.Json `json:"data"`
 }
+
+type annotationType int
+
+const (
+	Global annotationType = iota
+	Local
+)
+
+func (annotation *ItemDTO) GetType() annotationType {
+	if annotation.DashboardId != 0 {
+		return Local
+	}
+	return Global
+}