Move Channels into App (#18623)

* Move Channels into App

In this PR, we make Channels as part of App
instead of Server. This is part of the transition period
of moving fields from Server to Channels.

For now, Channels contains Server. So the hierarchy is

App -> Channels -> Server.

And as a first step, we also move httpService to Channels.

```release-note
NONE
```

* Fixing another test

```release-note
NONE
```

* new method

```release-note
NONE
```

app/server.go

@@ -162,8 +162,6 @@ type Server struct {
 
 	phase2PermissionsMigrationComplete bool
 
-	httpService httpservice.HTTPService
-
 	ImageProxy *imageproxy.ImageProxy
 
 	Audit            *audit.Audit
@@ -267,9 +265,19 @@ func NewServer(options ...Option) (*Server, error) {
 	// This is called after initLogging() to avoid a race condition.
 	mlog.Info("Server is initializing...", mlog.String("go_version", runtime.Version()))
 
+	// Initialize products
+	for name, initializer := range products {
+		prod, err := initializer(s)
+		if err != nil {
+			return nil, errors.Wrapf(err, "error initializing product: %s", name)
+		}
+
+		s.products[name] = prod
+	}
+
 	// It is important to initialize the hub only after the global logger is set
 	// to avoid race conditions while logging from inside the hub.
-	app := New(ServerConnector(s))
+	app := New(ServerConnector(s.Channels()))
 	app.HubStart()
 
 	if *s.Config().LogSettings.EnableDiagnostics && *s.Config().LogSettings.EnableSentry {
@@ -304,8 +312,7 @@ func NewServer(options ...Option) (*Server, error) {
 		s.tracer = tracer
 	}
 
-	s.httpService = httpservice.MakeHTTPService(s)
-	s.pushNotificationClient = s.httpService.MakeClient(true)
+	s.pushNotificationClient = s.Channels().HTTPService().MakeClient(true)
 
 	s.ImageProxy = imageproxy.MakeImageProxy(s, s.HTTPService(), s.Log)
 
@@ -349,6 +356,7 @@ func NewServer(options ...Option) (*Server, error) {
 		return nil, errors.Wrapf(err2, "unable to load Mattermost translation files")
 	}
 
+	// initEnterprise needs to be called after products initialization.
 	s.initEnterprise()
 
 	if s.newStore == nil {
@@ -695,16 +703,6 @@ func NewServer(options ...Option) (*Server, error) {
 		}
 	})
 
-	// Initialize products
-	for name, initializer := range products {
-		prod, err := initializer(s)
-		if err != nil {
-			return nil, errors.Wrapf(err, "error initializing product: %s", name)
-		}
-
-		s.products[name] = prod
-	}
-
 	s.AddConfigListener(func(oldCfg, newCfg *model.Config) {
 		if !oldCfg.FeatureFlags.TimedDND && newCfg.FeatureFlags.TimedDND {
 			runDNDStatusExpireJob(app)
@@ -788,10 +786,15 @@ func (s *Server) runJobs() {
 // Global app options that should be applied to apps created by this server
 func (s *Server) AppOptions() []AppOption {
 	return []AppOption{
-		ServerConnector(s),
+		ServerConnector(s.Channels()),
 	}
 }
 
+func (s *Server) Channels() *Channels {
+	ch, _ := s.products["channels"].(*Channels)
+	return ch
+}
+
 // Return Database type (postgres or mysql) and current version of Mattermost
 func (s *Server) DatabaseTypeAndMattermostVersion() (string, string) {
 	mattermostVersion, _ := s.Store.System().GetByName("Version")
@@ -1957,7 +1960,7 @@ func (s *Server) TelemetryId() string {
 }
 
 func (s *Server) HTTPService() httpservice.HTTPService {
-	return s.httpService
+	return s.Channels().HTTPService()
 }
 
 func (s *Server) SetLog(l *mlog.Logger) {
@@ -2258,18 +2261,18 @@ func (s *Server) ReadFile(path string) ([]byte, *model.AppError) {
 // }
 
 func createDNDStatusExpirationRecurringTask(a *App) {
-	a.srv.dndTaskMut.Lock()
-	a.srv.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, 5*time.Minute)
-	a.srv.dndTaskMut.Unlock()
+	a.ch.srv.dndTaskMut.Lock()
+	a.ch.srv.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, 5*time.Minute)
+	a.ch.srv.dndTaskMut.Unlock()
 }
 
 func cancelDNDStatusExpirationRecurringTask(a *App) {
-	a.srv.dndTaskMut.Lock()
-	if a.srv.dndTask != nil {
-		a.srv.dndTask.Cancel()
-		a.srv.dndTask = nil
+	a.ch.srv.dndTaskMut.Lock()
+	if a.ch.srv.dndTask != nil {
+		a.ch.srv.dndTask.Cancel()
+		a.ch.srv.dndTask = nil
 	}
-	a.srv.dndTaskMut.Unlock()
+	a.ch.srv.dndTaskMut.Unlock()
 }
 
 func runDNDStatusExpireJob(a *App) {
@@ -2279,7 +2282,7 @@ func runDNDStatusExpireJob(a *App) {
 	if a.IsLeader() {
 		createDNDStatusExpirationRecurringTask(a)
 	}
-	a.srv.AddClusterLeaderChangedListener(func() {
+	a.ch.srv.AddClusterLeaderChangedListener(func() {
 		mlog.Info("Cluster leader changed. Determining if unset DNS status task should be running", mlog.Bool("isLeader", a.IsLeader()))
 		if a.IsLeader() {
 			createDNDStatusExpirationRecurringTask(a)