Rejoin server with lobby

[AdmiralbadBeef]

Feature request: Ability to rejoin a world with a lobby/proxy server that requires a "/server XXXXXX" command to join a world

also worth noting usually when d/c due to server restart you are booted out to the lobby not out of the server entirely.

[AMereBagatelle]

Coming back to this after a few months, there are a few issues to observe in adding this:

1. I don't know where to get the context for which server/world to rejoin, maybe this could be solved by user specification.
2. I can't detect when a client changes worlds, or at the very least it's near impossible to be able to tell a world switch apart from normal dimension changes from what I can tell.