wxiaoguang 1c8bc4081a

Show friendly 500 error page to users and developers (#24110) ...

Close #24104

This also introduces many tests to cover many complex error handling
functions.

### Before

The details are never shown in production.

<details>

![image](https://user-images.githubusercontent.com/2114189/231805004-13214579-4fbe-465a-821c-be75c2749097.png)

</details>

### After

The details could be shown to site admin users. It is safe.

![image](https://user-images.githubusercontent.com/2114189/231803912-d5660994-416f-4b27-a4f1-a4cc962091d4.png)

2023-04-14 13:19:11 +08:00

..

404.tmpl

Show friendly 500 error page to users and developers (#24110)

2023-04-14 13:19:11 +08:00

500.tmpl

Show friendly 500 error page to users and developers (#24110)

2023-04-14 13:19:11 +08:00