Record Case Detail - VG101 FA2021 (Jigang) - JOJ

This function is in beta test. Please help improve it in the issues here.

Welcome to the library management system, please type your commands.
> 
Test1 added to the system.
> 
1 Test1 on shelf
> 
The book ID already exists.
> 
1 Test1 on shelf
> 
c1 added to the system.
> 
1 c1
> 
The customer ID already exists.
> 
1 c1
> 
Exit the system!

Welcome to the library management system, please type your commands.
> Test1 added to the system.
> 1 Test1 on shelf
> The book ID already exists.
> 1 Test1 on shelf
> c1 added to the system.
> 1 c1
> The customer ID already exists.
> 1 c1
> Exit the system!