Whitelisting1

[Mabeeck]

Pull request for whitelisting functionality on the server side.
No commands will be included in this PR.
Does some progress with #2566.

I might still need some help to handle rejecting the connection better.

• Fix: [error]: Encountered error while opening world: DisconnectedByServer on client, when connection is rejected
• Get rid of [info]: Disconnected (x2) in server logs when rejecting a connection
• Prevent player file creation for rejected connection requests

[Wunka]

The struct is probably from the times when it had a few more fields and this is still a draft so don't take my requested changes to hard.

I have not yet tested your code (it still a draft I don't require it to already work perfectly)

[Wunka]

Get rid of [info]: Disconnected (x2) in server logs when rejecting a connection

I think this happens not only in your PR. So if you can get rid of it 🎉 but don't focus on it