changelog updates for 2.6.0-rc1

publish the FORWARD 005 token

close remaining 2.6 issues

Warn users that NS UNREGISTER doesn't give them a "do-over";
the account name will remain reserved.

UBAN ADD and DEL need to produce snomasks and loglines

Document permissions structure of CS AMODE

CS INFO with no arguments should list your registered channels

simplify semaphore release code

fix #1592

Implements the new `CHATHISTORY LISTCORRESPONDENTS` API.

try to record buntdb errors from persisting lastSeen

Potentially fixes the database corruption seen on #1603

See #1603

fix #1594

fix #1576

1. Use FAIL instead of WARN
2. Use NICKNAME_RESERVED instead of ACCOUNT_REQUIRED
3. Don't send 433 at all for registered clients, just send the FAIL

List IRCv3 CAPs in `NS CLIENTS LIST` output

Send a WARN NICK ACCOUNT_REQUIRED on attempt to take a reserved nick

fix #1596

All truncation must be made UTF8-safe.

fix #1531

Fix #1562

AWAY status should be tracked per-session:

1. With auto-away enabled, away status is aggregated across sessions
   (if any session is not away, the client is not away, else use
   the away status that was set most recently)
2. With auto-away disabled, we get the legacy behavior where AWAY
   applies directly to the client

Implement the new bot mode spec:
https://github.com/ircv3/ircv3-specifications/pull/439

some small fixes/enhancements

RELAYMSG should respect mutes

Improve error message for CS TRANSFER

PerstentStatusMandatory should display as "enabled", not "mandatory",
in the context where it refers to a user-chosen setting.

Allow chanops to delete channel messages from history

Handle panics in rehash, even if it was triggered by SIGHUP

bump irc-go again

Fix link to productionizing guide.