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/services/sqlstore/migrations/dashboard_mig.go

@@ -230,4 +230,8 @@ func addDashboardMigration(mg *Migrator) {
 		Cols: []string{"is_folder"},
 		Type: IndexType,
 	}))
+
+	mg.AddMigration("Add isPublic for dashboard", NewAddColumnMigration(dashboardV2, &Column{
+		Name: "is_public", Type: DB_Bool, Nullable: false, Default: "0",
+	}))
 }