Add support for utf8-only

Add support for account-tag

Slightly relax new log file permissions

Make new log files group-readable by default. To retain the prior
behavior, soju can be started with a umask set to 0077.

contrib/clients: add reference to Weechat script

doc/soju.1: explain http-origin defaults

Don't suggest users to /motd in multi-upstream mode

Make user MODE commands fail in multi-upstream mode

References: https://todo.sr.ht/~emersion/soju/20

Forward user mode changes in single-upstream mode

References: https://todo.sr.ht/~emersion/soju/20

Forward MOTD messages downstream

The first MOTD upon connection is ignored, but subsequent MOTD messages
(requested by the "MOTD" message from the client, typically using a
/motd command) are forwarded.

Add downstreamConn.SendBatch helper

Prune detached channels from CHATHISTORY TARGETS

Implement CHATHISTORY TARGETS

References: https://github.com/ircv3/ircv3-specifications/pull/450

doc/ext/bouncer-networks: fix typo

Forward unknown commands to upstream in single-upstream mode

Send placeholder when no network/channel is returned by BouncerServ

Reject JOIN with invalid channel names

This prevents us from storing typo'ed channel names in the DB.

Fix typo in BOUNCER notifications: s/status/state/

Broadcast BOUNCER notifications to all downstream connections

We weren't sending them to downstreams which weren't bound to a
network.

Allow networks to be disabled

doc/getting-started: s/Freenode/Libera Chat/