MM-10658 Change config fields to pointers (#9033)

* MM 10658 Change config fields to pointers (#8898)

* Change fields of config structs to pointers and set defaults

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Fix tests that go broken during switching config structs to pointers

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Apply changes of current master while switching config structs to pointers

MM-10658 https://github.com/mattermost/mattermost-server/issues/8841

* Fix new config pointer uses

* Fix app tests

* Fix mail test

* remove debugging statement

* fix TestUpdateConfig

* assign config consistently

* initialize AmazonS3Region in TestS3TestConnection

* initialize fields for TestEmailTest

* fix TestCheckMandatoryS3Fields

api4/oauth.go

@@ -325,7 +325,7 @@ func deauthorizeOAuthApp(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func authorizeOAuthPage(c *Context, w http.ResponseWriter, r *http.Request) {
-	if !c.App.Config().ServiceSettings.EnableOAuthServiceProvider {
+	if !*c.App.Config().ServiceSettings.EnableOAuthServiceProvider {
 		err := model.NewAppError("authorizeOAuth", "api.oauth.authorize_oauth.disabled.app_error", nil, "", http.StatusNotImplemented)
 		utils.RenderWebAppError(c.App.Config(), w, r, err, c.App.AsymmetricSigningKey())
 		return