Alerting: Support simplified routing receivers in Prometheus conversion API (#105135)

Adds ability to set notifications settings using the Prometheus conversion API.

The API now supports a new optional header: X-Grafana-Alerting-Notification-Settings which can be used to specify notification settings.

The value of the header is the AlertRuleNotificationSettings structure in JSON:
mimirtool rules load alerts.yaml --extra-headers 'X-Grafana-Alerting-Notification-Settings: {"receiver": "my-webhook", "group_by": ["cluster", "pod"]}'

pkg/services/ngalert/api/api_convert_prometheus_test.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"context"
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -425,6 +426,97 @@ func TestRouteConvertPrometheusPostRuleGroup(t *testing.T) {
 		require.NotNil(t, remaining[0].Record)
 		require.Equal(t, targetDSUID, remaining[0].Record.TargetDatasourceUID)
 	})
+
+	t.Run("sets notification settings for rules if specified", func(t *testing.T) {
+		srv, _, ruleStore, _ := createConvertPrometheusSrv(t)
+		rc := createRequestCtx()
+
+		receiver := "test-receiver"
+		groupBy := []string{"cluster", "pod"}
+		settings := apimodels.AlertRuleNotificationSettings{
+			Receiver: receiver,
+			GroupBy:  groupBy,
+		}
+		settingsJSON, err := json.Marshal(settings)
+		require.NoError(t, err)
+		rc.Req.Header.Set(notificationSettingsHeader, string(settingsJSON))
+
+		simpleGroup := apimodels.PrometheusRuleGroup{
+			Name:     "Test Group",
+			Interval: prommodel.Duration(1 * time.Minute),
+			Rules: []apimodels.PrometheusRule{
+				{
+					Alert: "TestAlert",
+					Expr:  "up == 0",
+					For:   util.Pointer(prommodel.Duration(5 * time.Minute)),
+					Labels: map[string]string{
+						"severity": "critical",
+					},
+				},
+			},
+		}
+
+		response := srv.RouteConvertPrometheusPostRuleGroup(rc, "test", simpleGroup)
+		require.Equal(t, http.StatusAccepted, response.Status())
+
+		createdRules, err := ruleStore.ListAlertRules(context.Background(), &models.ListAlertRulesQuery{
+			OrgID: 1,
+		})
+		require.NoError(t, err)
+		require.Len(t, createdRules, 1)
+		require.Len(t, createdRules[0].NotificationSettings, 1)
+		require.Equal(t, receiver, createdRules[0].NotificationSettings[0].Receiver)
+		require.Equal(t, groupBy, createdRules[0].NotificationSettings[0].GroupBy)
+	})
+
+	t.Run("returns error when notification settings header contains invalid JSON", func(t *testing.T) {
+		srv, _, _, _ := createConvertPrometheusSrv(t)
+		rc := createRequestCtx()
+
+		rc.Req.Header.Set(notificationSettingsHeader, "{invalid json")
+
+		simpleGroup := apimodels.PrometheusRuleGroup{
+			Name:     "Test Group",
+			Interval: prommodel.Duration(1 * time.Minute),
+			Rules: []apimodels.PrometheusRule{
+				{
+					Alert: "TestAlert",
+					Expr:  "up == 0",
+				},
+			},
+		}
+
+		response := srv.RouteConvertPrometheusPostRuleGroup(rc, "test", simpleGroup)
+		require.Equal(t, http.StatusBadRequest, response.Status())
+		require.Contains(t, string(response.Body()), "Invalid value for header X-Grafana-Alerting-Notification-Settings")
+	})
+
+	t.Run("returns error when notification settings contain invalid values", func(t *testing.T) {
+		srv, _, _, _ := createConvertPrometheusSrv(t)
+		rc := createRequestCtx()
+
+		settings := apimodels.AlertRuleNotificationSettings{
+			Receiver: "", // empty receiver is invalid
+		}
+		settingsJSON, err := json.Marshal(settings)
+		require.NoError(t, err)
+		rc.Req.Header.Set(notificationSettingsHeader, string(settingsJSON))
+
+		simpleGroup := apimodels.PrometheusRuleGroup{
+			Name:     "Test Group",
+			Interval: prommodel.Duration(1 * time.Minute),
+			Rules: []apimodels.PrometheusRule{
+				{
+					Alert: "TestAlert",
+					Expr:  "up == 0",
+				},
+			},
+		}
+
+		response := srv.RouteConvertPrometheusPostRuleGroup(rc, "test", simpleGroup)
+		require.Equal(t, http.StatusBadRequest, response.Status())
+		require.Contains(t, string(response.Body()), "Invalid value for header X-Grafana-Alerting-Notification-Settings")
+	})
 }
 
 func TestRouteConvertPrometheusGetRuleGroup(t *testing.T) {