[Alerting]: Extend quota service to optionally set limits on alerts (#33283)

* Quota: Extend service to set limit on alerts

* Add test for applying quota to alert rules

* Apply suggestions from code review

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Get used alert quota only if naglert is enabled

* Set alert limit to zero if nglalert is not enabled
Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

pkg/services/ngalert/api/api.go

@@ -3,6 +3,8 @@ package api
 import (
 	"time"
 
+	"github.com/grafana/grafana/pkg/services/quota"
+
 	"github.com/grafana/grafana/pkg/services/ngalert/metrics"
 	"github.com/grafana/grafana/pkg/services/ngalert/state"
 
@@ -41,6 +43,7 @@ type API struct {
 	DatasourceCache datasources.CacheService
 	RouteRegister   routing.RouteRegister
 	DataService     *tsdb.Service
+	QuotaService    *quota.QuotaService
 	Schedule        schedule.ScheduleService
 	RuleStore       store.RuleStore
 	InstanceStore   store.InstanceStore
@@ -73,7 +76,7 @@ func (api *API) RegisterAPIEndpoints(m *metrics.Metrics) {
 	api.RegisterRulerApiEndpoints(NewForkedRuler(
 		api.DatasourceCache,
 		NewLotexRuler(proxy, logger),
-		RulerSrv{DatasourceCache: api.DatasourceCache, manager: api.StateManager, store: api.RuleStore, log: logger},
+		RulerSrv{DatasourceCache: api.DatasourceCache, QuotaService: api.QuotaService, manager: api.StateManager, store: api.RuleStore, log: logger},
 	), m)
 	api.RegisterTestingApiEndpoints(TestingApiSrv{
 		AlertingProxy:   proxy,