增加 SSO 示例（增加注释）

lab-68/lab-68-demo21-authorization-server-on-sso/src/main/resources/db/oauth_data.sql

@@ -4,4 +4,4 @@ INSERT INTO oauth_client_details
 	refresh_token_validity, additional_information, autoapprove)
 VALUES
 	('clientapp', '112233', 'read_userinfo,read_contacts',
-	'password,refresh_token', null, null, 3600, 864000, null, true);
+	'password,authorization_code,refresh_token', 'http://127.0.0.1:9090/login', null, 3600, 864000, null, true);

lab-68/lab-68-demo21-resource-server-on-sso/src/main/java/cn/iocoder/springboot/lab68/resourceserverdemo/controller/DemoController.java

@@ -13,13 +13,13 @@ import org.springframework.web.bind.annotation.RestController;
 public class DemoController {
 
     @GetMapping("/admin-list")
-    @PreAuthorize("hasRole('ADMIN')")
+    @PreAuthorize("hasRole('ADMIN')") // 要求管理员 ROLE_ADMIN 角色
     public String adminList() {
         return "管理员列表";
     }
 
     @GetMapping("/user-list")
-    @PreAuthorize("hasRole('USER')")
+    @PreAuthorize("hasRole('USER')") // 要求普通用户 ROLE_USER 角色
     public String userList() {
         return "用户列表";
     }

lab-68/《芋道 Spring Security OAuth2 单点登陆》.md

@@ -0,0 +1 @@
+<http://www.iocoder.cn/Spring-Security/OAuth2-learning-sso/?github>