Alerting: Add endpoint to revert to a previous alertmanager configuration (#65751)

* Alerting: Add endpoint to revert to a previous alertmanager configuration

This endpoint is meant to be used in conjunction with /api/alertmanager/grafana/config/history to
revert to a previously applied alertmanager configuration. This is done by ID instead of raw config
string in order to avoid secure field complications.

pkg/services/ngalert/api/tooling/definitions/alertmanager.go

@@ -61,6 +61,15 @@ import (
 //     Responses:
 //       200: GettableHistoricUserConfigs
 
+// swagger:route POST /api/alertmanager/grafana/config/history/{id}/_activate alertmanager RoutePostGrafanaAlertingConfigHistoryActivate
+//
+// revert Alerting configuration to the historical configuration specified by the given id
+//
+//     Responses:
+//       202: Ack
+//       400: ValidationError
+//       404: NotFound
+
 // swagger:route DELETE /api/alertmanager/grafana/config/api/v1/alerts alertmanager RouteDeleteGrafanaAlertingConfig
 //
 // deletes the Alerting config for a tenant
@@ -458,6 +467,13 @@ type BodyAlertingConfig struct {
 	Body PostableUserConfig
 }
 
+// swagger:parameters RoutePostGrafanaAlertingConfigHistoryActivate
+type HistoricalConfigId struct {
+	// Id should be the id of the GettableHistoricUserConfig
+	// in:path
+	Id int64 `json:"id"`
+}
+
 // alertmanager routes
 // swagger:parameters RoutePostAlertingConfig RouteGetAlertingConfig RouteDeleteAlertingConfig RouteGetAMStatus RouteGetAMAlerts RoutePostAMAlerts RouteGetAMAlertGroups RouteGetSilences RouteCreateSilence RouteGetSilence RouteDeleteSilence RoutePostAlertingConfig
 // testing routes