BanManager is incompatible with reverse-proxying and load balancing

[Geod24]

If someone wished to setup a reverse proxy in front of Agora, it would probably come crashing as soon as the BanManager would be involved, as it would end up banning the proxy. I suggest that we had a (configured) whitelist (we need a whitelisting mechanism for #1674 anyways) and handle https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For and https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded correctly.