Alerting: create wrapper for Alertmanager to enable org level isolation (#37320)

Introduces org-level isolation for the Alertmanager and its components.

Silences, Alerts and Contact points are not separated by org and are not shared between them.

Co-authored with @davidmparrott and @papagian

pkg/tests/api/alerting/api_alertmanager_configuration_test.go

@@ -6,6 +6,9 @@ import (
 	"net/http"
 	"regexp"
 	"testing"
+	"time"
+
+	"github.com/grafana/grafana/pkg/services/ngalert/notifier"
 
 	"github.com/grafana/grafana/pkg/bus"
 	"github.com/grafana/grafana/pkg/models"
@@ -16,6 +19,13 @@ import (
 )
 
 func TestAlertmanagerConfigurationIsTransactional(t *testing.T) {
+	// TODO: We need a reliable way to ensure Alertmanagers have synced correctly.
+	// For now, make them sync quicker.
+	p := notifier.SyncOrgsPollInterval
+	notifier.SyncOrgsPollInterval = 2 * time.Second
+	t.Cleanup(func() {
+		notifier.SyncOrgsPollInterval = p
+	})
 	dir, path := testinfra.CreateGrafDir(t, testinfra.GrafanaOpts{
 		EnableFeatureToggles: []string{"ngalert"},
 		DisableAnonymous:     true,
@@ -85,7 +95,7 @@ func TestAlertmanagerConfigurationIsTransactional(t *testing.T) {
 }
 `
 		resp := postRequest(t, alertConfigURL, payload, http.StatusBadRequest) // nolint
-		require.JSONEq(t, `{"message":"failed to save and apply Alertmanager configuration: the receiver is invalid: failed to validate receiver \"slack.receiver\" of type \"slack\": token must be specified when using the Slack chat API"}`, getBody(t, resp.Body))
+		require.JSONEq(t, `{"message":"failed to save and apply Alertmanager configuration: failed to build integration map: the receiver is invalid: failed to validate receiver \"slack.receiver\" of type \"slack\": token must be specified when using the Slack chat API"}`, getBody(t, resp.Body))
 
 		resp = getRequest(t, alertConfigURL, http.StatusOK) // nolint
 		require.JSONEq(t, defaultAlertmanagerConfigJSON, getBody(t, resp.Body))
@@ -94,6 +104,13 @@ func TestAlertmanagerConfigurationIsTransactional(t *testing.T) {
 	// editor42 from organisation 42 posts configuration
 	alertConfigURL = fmt.Sprintf("http://editor-42:editor-42@%s/api/alertmanager/grafana/config/api/v1/alerts", grafanaListedAddr)
 
+	// Before we start operating, make sure we've synced this org.
+	require.Eventually(t, func() bool {
+		resp, err := http.Get(alertConfigURL) // nolint
+		require.NoError(t, err)
+		return resp.StatusCode == http.StatusOK
+	}, 10*time.Second, 2*time.Second)
+
 	// Post the alertmanager config.
 	{
 		mockChannel := newMockNotificationChannel(t, grafanaListedAddr)