[MM-39820] Add AppBarEnabled feature flag (#18967)

Automatic Merge

model/feature_flags.go

@@ -25,9 +25,12 @@ type FeatureFlags struct {
 	// Enable the remote cluster service for shared channels.
 	EnableRemoteClusterService bool
 
-	// AppsEnabled toggle the Apps framework functionalities both in server and client side
+	// AppsEnabled toggles the Apps framework functionalities both in server and client side
 	AppsEnabled bool
 
+	// AppBarEnabled toggles the App Bar component on client side
+	AppBarEnabled bool
+
 	// Feature flags to control plugin versions
 	PluginPlaybooks  string `plugin_id:"playbooks"`
 	PluginApps       string `plugin_id:"com.mattermost.apps"`
@@ -69,6 +72,7 @@ func (f *FeatureFlags) SetDefaults() {
 	f.CollapsedThreads = true
 	f.EnableRemoteClusterService = false
 	f.AppsEnabled = false
+	f.AppBarEnabled = false
 	f.PluginApps = ""
 	f.PluginFocalboard = ""
 	f.PermalinkPreviews = true