`SUBSTRING` enhancement

[crwen]

Bug Report

What version of KipSQL are you using?

latest

What version of Rust are you using?

1.77.0

What's the status of the running?

What did you do?
When I run a SUBSTRING function that length is larger than the string, the connectionn is reseted.

What did you expect to see?

=> select substring('abc', 1, 10);
---------------------------------
 abc

What did you see instead?

=> select substring('abc', 1, 10);
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
The connection to the server was lost. Attempting reset: Succeeded.

I think it's better to handle this by retrieving all the characters after the start index(like PostgreSQL and MySQL)

[KKould]

ops, a connection reset probably means a panic has occurred. I'll try to fix it, thank you for your report

[KKould]

fixed on: #161