add isPublic to dashboard (#48012)

adds toggle to make a dashboard public

* config struct for public dashboard config
* api endpoints for public dashboard configuration
* ui for toggling public dashboard on and off
* load public dashboard config on share modal

Co-authored-by: Owen Smallwood <owen.smallwood@grafana.com>
Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

pkg/api/dtos/dashboard.go

@@ -33,6 +33,7 @@ type DashboardMeta struct {
 	Provisioned            bool                  `json:"provisioned"`
 	ProvisionedExternalId  string                `json:"provisionedExternalId"`
 	AnnotationsPermissions *AnnotationPermission `json:"annotationsPermissions"`
+	IsPublic               bool                  `json:"isPublic"`
 }
 type AnnotationPermission struct {
 	Dashboard    AnnotationActions `json:"dashboard"`