Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/app/platform/cluster_discovery_test.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package platform
+
+import (
+	"testing"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+)
+
+func TestClusterDiscoveryService(t *testing.T) {
+	th := Setup(t)
+	defer th.TearDown()
+
+	ds := th.Service.NewClusterDiscoveryService()
+	ds.Type = model.CDSTypeApp
+	ds.ClusterName = "ClusterA"
+	ds.AutoFillHostname()
+
+	ds.Start()
+	time.Sleep(2 * time.Second)
+
+	ds.Stop()
+	time.Sleep(2 * time.Second)
+}