Role refactor (#7867)

* role refactor

* add missing file

* fix web test

app/role.go

@@ -0,0 +1,19 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/utils"
+)
+
+func (a *App) Role(id string) *model.Role {
+	return a.roles[id]
+}
+
+// Updates the roles based on the app config and the global license check. You may need to invoke
+// this when license changes are made.
+func (a *App) SetDefaultRolesBasedOnConfig() {
+	a.roles = utils.DefaultRolesBasedOnConfig(a.Config())
+}