Destroy socket on client close

[martijnimhoff]

Fixes: #249

[martijnimhoff]

We can actually use .destroy() without .end().

Rationale for using destroy:

The docs say .end half closes the socket and .destroy will release any internal resources. I tried it with just a .destroy and checked the FTP logs to see what happens. I still get the following:

Thu Feb 22 14:57:07 2024 FTP command: Client "172.17.0.1", "QUIT"
Thu Feb 22 14:57:07 2024 FTP response: Client "172.17.0.1", "221 Goodbye."

It seems the connection is still closed gracefully? Therefore I think it is safe to use .destroy.

(I've also tested if this works when closing a client and then using access to re-establish the connecting again, I had no issues there)

[martijnimhoff]

I've also added a prepare command. In this way I can install my fork without having to publish it. Based on this answer:
https://stackoverflow.com/a/57829251/5688047

[patrickjuchli]

Thanks for this! I agree, let's go with destroy immediately. Good to keep the doNothing handler for any errors.

For future PRs: Try to limit your PR to exactly the described issue. You've included some other things. I'll make an exception and merge them as well, but try to avoid that next time/elsewhere.