[MM-44056] Make Calls plugin's state on Cloud controllable by feature flag (#20161)

* Make Calls plugin's state on Cloud controllable by feature flag

* Prepackage Calls v0.4.9 (#20148)

* Update app/plugin.go

Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>

* Update app/plugin_install.go

Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>

* Bump Calls version to latest

Co-authored-by: Jesse Hallam <jesse.hallam@gmail.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/feature_flags.go

@@ -32,12 +32,16 @@ type FeatureFlags struct {
 	PluginPlaybooks  string `plugin_id:"playbooks"`
 	PluginApps       string `plugin_id:"com.mattermost.apps"`
 	PluginFocalboard string `plugin_id:"focalboard"`
+	PluginCalls      string `plugin_id:"com.mattermost.calls"`
 
 	PermalinkPreviews bool
 
 	// Enable Calls plugin support in the mobile app
 	CallsMobile bool
 
+	// CallsEnabled controls whether or not the Calls plugin should be enabled
+	CallsEnabled bool
+
 	// A dash separated list for feature flags to turn on for Boards
 	BoardsFeatureFlags string
 
@@ -93,6 +97,7 @@ func (f *FeatureFlags) SetDefaults() {
 	f.CloudFree = false
 	f.CommandPalette = false
 }
+
 func (f *FeatureFlags) Plugins() map[string]string {
 	rFFVal := reflect.ValueOf(f).Elem()
 	rFFType := reflect.TypeOf(f).Elem()