Fix IRC listener relay of bodies and modes, and JOIN names (closes #127)

The IRC listener relayed only the first line of a PRIVMSG or NOTICE
body; it now sends one line per body line. A relayed MODE change now
carries its key, limit or mask, each value its own parameter, also in
the echo to the user who made it. CR, LF and NUL are removed from each
parameter and from each whole line sent to an IRC listener connection,
so no stored value can start a line of its own. The channel name check
moved into service.JoinChannel, so the IRC listener's JOIN refuses the
same names with 403.

Model: opus-5-5

README.md

@@ -2667,7 +2667,9 @@ IRC_LISTEN_ADDR: ""
 - **CAP negotiation**: `CAP LS` gets an empty capability list and `CAP END` is
   ignored, for compatibility with modern clients.
 - **Channel prefixes**: Channels must start with `#`. `JOIN` prepends it if
-  omitted; other commands use the name as given.
+  omitted; other commands use the name as given. As over the HTTP API, `JOIN`
+  answers a name that is not `#` followed by 1–63 letters, digits, `_` or `-`
+  with ERR_NOSUCHCHANNEL (403).
 - **First joiner**: The first user to join a channel is automatically granted
   operator status (`@`).
 - **Channel modes**: `+i` (invite-only), `+m` (moderated), `+n` (no external),
@@ -2689,21 +2691,20 @@ IRC_LISTEN_ADDR: ""
 Messages sent by IRC clients appear in channels visible to HTTP/JSON API clients
 and vice versa. The IRC listener and HTTP API share the same database, broker,
 and session infrastructure, so a user connected via IRC and a user connected via
-the HTTP API can talk in the same channels, with these gaps today:
+the HTTP API can talk in the same channels.
 
-- An IRC listener user receives only the first line of a multi-line `body`.
-- A `+k`, `+l` or `+b` change made over the HTTP API reaches IRC listener
-  members without its key, limit or mask.
-- The IRC listener's `JOIN` accepts any channel name, while over the HTTP API a
-  name that is not `#` followed by 1–63 letters, digits, `_` or `-` gets
-  ERR_NOSUCHCHANNEL (403), so HTTP API users cannot join such a channel.
-- The IRC listener does not pass on a `PRIVMSG`, `NOTICE`, `JOIN`, `PART`,
-  `NICK` or `QUIT` whose sender's nick matches the user's own nick ignoring
-  case, so an IRC listener user `alice` never sees these from `Alice`, although
-  nicks are case-sensitive.
+Each line of a multi-line `body` reaches an IRC listener user as its own
+`PRIVMSG` or `NOTICE` line. A CR, LF or NUL inside a line is removed before it
+is sent, so it cannot start a line of its own. A mode change made over the HTTP
+API reaches IRC listener members as an IRC `MODE` line with its value as a
+separate parameter, e.g. `MODE #general +k secretpass` or
+`MODE #general +o bob`.
 
-https://git.eeqj.de/sneak/neoirc/issues/127 tracks the first three and
-https://git.eeqj.de/sneak/neoirc/issues/128 the last.
+One gap remains: the IRC listener does not pass on a `PRIVMSG`, `NOTICE`,
+`JOIN`, `PART`, `NICK` or `QUIT` whose sender's nick matches the user's own nick
+ignoring case, so an IRC listener user `alice` never sees these from `Alice`,
+although nicks are case-sensitive. https://git.eeqj.de/sneak/neoirc/issues/128
+tracks it.
 
 ### Docker Usage