Add GetFileLink method to plugin API (#9665)

* add GetFileLink method to plugin API

* Update plugin/api.go

* add translations for new plugin API errors

app/plugin_api.go

@@ -369,6 +369,23 @@ func (api *PluginAPI) GetFileInfo(fileId string) (*model.FileInfo, *model.AppErr
 	return api.app.GetFileInfo(fileId)
 }
 
+func (api *PluginAPI) GetFileLink(fileId string) (string, *model.AppError) {
+	if !api.app.Config().FileSettings.EnablePublicLink {
+		return "", model.NewAppError("GetFileLink", "plugin_api.get_file_link.disabled.app_error", nil, "", http.StatusNotImplemented)
+	}
+
+	info, err := api.app.GetFileInfo(fileId)
+	if err != nil {
+		return "", err
+	}
+
+	if len(info.PostId) == 0 {
+		return "", model.NewAppError("GetFileLink", "plugin_api.get_file_link.no_post.app_error", nil, "file_id="+info.Id, http.StatusBadRequest)
+	}
+
+	return api.app.GeneratePublicLink(api.app.GetSiteURL(), info), nil
+}
+
 func (api *PluginAPI) ReadFile(path string) ([]byte, *model.AppError) {
 	return api.app.ReadFile(path)
 }