Add exception handling in the samples program

[amrnyang]

I have been researching Spring authorization servers and Spring security recently. I have read the source code of the demonstration authorization server in the Spring authorization server example. I tried to build an authorization server independently, but encountered difficulties in mastering the exception handling mechanism. I have conducted extensive research and studied the exception handling mechanism of Spring Security and made several attempts, but I am unable to solve this problem. I simulated database connection failure and 1/0 exception during the login process. GlobalExceptionAdvice (a self written exception handling class) did not handle these two exceptions. Can we consider adding enhanced exception handling to the demo authorization server in the upcoming update?I used three examples: demo-authorizationserver, demo-client, and messages-resource. Thanks!