MM-27199 - Add metrics to MM server for total enabled user count (#15116)

* Add metrics to MM server for total enabled user count and include installation ID from a new env var

* diagnostics context

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

jobs/interfaces/active_users_interface.go

@@ -0,0 +1,11 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package interfaces
+
+import "github.com/mattermost/mattermost-server/v5/model"
+
+type ActiveUsersJobInterface interface {
+	MakeWorker() model.Worker
+	MakeScheduler() model.Scheduler
+}