Alerting: Provisioning API respects global rule quota (#52180)

* Inject interface for quota service and create mock

* Check quota and return 403 if limit exceeded

* Implement tests for quota being exceeded

pkg/services/ngalert/api/api_ruler.go

@@ -42,7 +42,6 @@ type RulerSrv struct {
 }
 
 var (
-	errQuotaReached        = errors.New("quota has been exceeded")
 	errProvisionedResource = errors.New("request affects resources created via provisioning API")
 )
 
@@ -401,7 +400,7 @@ func (srv RulerSrv) updateAlertRulesInGroup(c *models.ReqContext, groupKey ngmod
 				return fmt.Errorf("failed to get alert rules quota: %w", err)
 			}
 			if limitReached {
-				return errQuotaReached
+				return ngmodels.ErrQuotaReached
 			}
 		}
 		return nil
@@ -412,7 +411,7 @@ func (srv RulerSrv) updateAlertRulesInGroup(c *models.ReqContext, groupKey ngmod
 			return ErrResp(http.StatusNotFound, err, "failed to update rule group")
 		} else if errors.Is(err, ngmodels.ErrAlertRuleFailedValidation) || errors.Is(err, errProvisionedResource) {
 			return ErrResp(http.StatusBadRequest, err, "failed to update rule group")
-		} else if errors.Is(err, errQuotaReached) {
+		} else if errors.Is(err, ngmodels.ErrQuotaReached) {
 			return ErrResp(http.StatusForbidden, err, "")
 		} else if errors.Is(err, ErrAuthorization) {
 			return ErrResp(http.StatusUnauthorized, err, "")