Implements #1577, but the issue should remain open until we clean up
the debugging loglines.

Improve debuggability of some config deserialization errors

If history is disabled, disable the history CAPs

Fixes #1510

Track channel join times, use them to optionally enforce history access
restrictions

Improve auditability of sensitive operator actions

strip local_ from oper capab names, also consolidate unban into ban

Add the new utf8-only cap, disallow non-utf8 when websockets are enabled

Fixes #810

Tor listeners should never see an STS cap.

Add an undocumented 'hide-sts' key for listeners that hides the STS cap.
This can be used if the listener is secured at layer 3 or 4 (VPNs,
E2E mixnets). It will be necessary to add the relevant IPs to `secure-nets`.

Fixes #1407

Support PROXY protocol v2, including ahead of plaintext connections

See #1171.

Add chanmode preventing speech to error message.

Fixes #1182.

See #1240.

See discussion on #68.

These should have been removed in #1027.

Since allocating them is rare.

Previously, we were applying defaults before the user had completed
registration. This meant that the number of invisible users was
incremented when the user connected, and then the total was incremented
when registration was completed.

Now both counters are updated at the same time. If a user disconnects
prior to registration, +i has not yet been applied so it would not be
decremented.