Feature Request : Add the possibility of activating a whitelist on a server

The current problem is that no discord server is really private, it only takes a leaked invitation link to find a potential intruder in our server. So my proposal would be to add a whitelist system by manually entering the desired member's discord tag (with maybe a way to send them an invitation automatically after adding them to the list). It could be a good way to make real private server between friends (maybe with always a way for the discord staff to connect to still check abnormal behavior on some servers).