Add fields to Server and LiveServer
Add fields to Server and LiveServer

LiveServer now has mfa_level, which is currently 0 (no MFA requirement
for admins) or 1 (at least 2FA required for admins).

Server now additionally has emojis, features, splash, and
default_message_notifications, with meanings equivalent to LiveServer.

jonalmeida/discord-rs,acdenisSK/discord-rs,SpaceManiac/discord-rs