[MM-16376] Allow server to download and install a plugin from… (#11372)

* Initial implementation of plugin remote source

* Implement API route

* Test API route

* Add i18n

* Handle different error cases in API route

* Include missing i18n translation

* Include AllowInsecureDownloadUrl in telemetry capture

* Updates from PR feedback

* Use HTTPService instead of http.Get

* Remove InstallPluginFromUrlForced from client4

* Use net/url library to inspect url scheme

* remove PluginDownloadUrl from web/params.go

* Allow plugin downloads from internal sources

model/config.go

@@ -2183,12 +2183,13 @@ type PluginState struct {
 }
 
 type PluginSettings struct {
-	Enable          *bool
-	EnableUploads   *bool   `restricted:"true"`
-	Directory       *string `restricted:"true"`
-	ClientDirectory *string `restricted:"true"`
-	Plugins         map[string]map[string]interface{}
-	PluginStates    map[string]*PluginState
+	Enable                   *bool
+	EnableUploads            *bool   `restricted:"true"`
+	AllowInsecureDownloadUrl *bool   `restricted:"true"`
+	Directory                *string `restricted:"true"`
+	ClientDirectory          *string `restricted:"true"`
+	Plugins                  map[string]map[string]interface{}
+	PluginStates             map[string]*PluginState
 }
 
 func (s *PluginSettings) SetDefaults(ls LogSettings) {
@@ -2200,6 +2201,10 @@ func (s *PluginSettings) SetDefaults(ls LogSettings) {
 		s.EnableUploads = NewBool(false)
 	}
 
+	if s.AllowInsecureDownloadUrl == nil {
+		s.AllowInsecureDownloadUrl = NewBool(false)
+	}
+
 	if s.Directory == nil {
 		s.Directory = NewString(PLUGIN_SETTINGS_DEFAULT_DIRECTORY)
 	}