Alerting: Add notification policy provisioning file export (#70009)

* Alerting: Add notification policy provisioning file export

- Add provisioning API endpoint for exporting notification policies.
- Add option in notification policy view ellipsis dropdown for exporting.
- Update various provisioning documentation.

pkg/services/ngalert/api/generated_base_api_provisioning.go

@@ -34,6 +34,7 @@ type ProvisioningApi interface {
 	RouteGetMuteTiming(*contextmodel.ReqContext) response.Response
 	RouteGetMuteTimings(*contextmodel.ReqContext) response.Response
 	RouteGetPolicyTree(*contextmodel.ReqContext) response.Response
+	RouteGetPolicyTreeExport(*contextmodel.ReqContext) response.Response
 	RouteGetTemplate(*contextmodel.ReqContext) response.Response
 	RouteGetTemplates(*contextmodel.ReqContext) response.Response
 	RoutePostAlertRule(*contextmodel.ReqContext) response.Response
@@ -113,6 +114,9 @@ func (f *ProvisioningApiHandler) RouteGetMuteTimings(ctx *contextmodel.ReqContex
 func (f *ProvisioningApiHandler) RouteGetPolicyTree(ctx *contextmodel.ReqContext) response.Response {
 	return f.handleRouteGetPolicyTree(ctx)
 }
+func (f *ProvisioningApiHandler) RouteGetPolicyTreeExport(ctx *contextmodel.ReqContext) response.Response {
+	return f.handleRouteGetPolicyTreeExport(ctx)
+}
 func (f *ProvisioningApiHandler) RouteGetTemplate(ctx *contextmodel.ReqContext) response.Response {
 	// Parse Path Parameters
 	nameParam := web.Params(ctx.Req)[":name"]
@@ -360,6 +364,16 @@ func (api *API) RegisterProvisioningApiEndpoints(srv ProvisioningApi, m *metrics
 				m,
 			),
 		)
+		group.Get(
+			toMacaronPath("/api/v1/provisioning/policies/export"),
+			api.authorize(http.MethodGet, "/api/v1/provisioning/policies/export"),
+			metrics.Instrument(
+				http.MethodGet,
+				"/api/v1/provisioning/policies/export",
+				api.Hooks.Wrap(srv.RouteGetPolicyTreeExport),
+				m,
+			),
+		)
 		group.Get(
 			toMacaronPath("/api/v1/provisioning/templates/{name}"),
 			api.authorize(http.MethodGet, "/api/v1/provisioning/templates/{name}"),