Add support for ircv3 WEBIRC command

[jhthorsen]

Some Convos admins and IRC servers want to see the real IP of the user, and not the IP of where Convos is running.

https://ircv3.net/specs/extensions/webirc is a way to solve this issue, but there is a problem: Convos has persistent connections and since the WEBIRC command can only be sent when connecting, the IP will never get updated until the user actively reconnects.

[jhthorsen]

From 1f9c23b:

Add EXPERIMENTAL support for https://ircv3.net/specs/extensions/webirc

This implementation allow a Convos admin to set an environment variable to enable WEBIRC. Example:

#!/bin/sh
export CONVOS_WEBIRC_PASSWORD_LOCALHOST=some_super_secret_password
export CONVOS_WEBIRC_PASSWORD_MY_SERVER=some_super_secret_password
./script/convos daemon

The part after "CONVOS_WEBIRC_PASSWORD_" is the connection ID, in upper case, without the "irc-" prefix and special characters (such as "-") translated into "_".

Setting the environment variable will cause the following IRC commmand to be sent to the server:

WEBIRC some_super_secret_password convos <hostname> <ip>

"hostname" will fallback to "ip" if the IP could not resolved.

IMPORTANT! The "ip" will only update after a USER has gone to the connection settings and hit "Update". The default "ip" (until a user have updated the settings) will be 127.0.0.1. Also, the "ip" will not get updated when the user change IP. It will only get updated when the user actively goes to the connection settings and hit "Update".

[jhthorsen]

Going to close this for now. Might get re-opened based on feedback.