feat(panettone): Bring back + fix irccat issue creation announcement

This reverts commit e1067b1497.

The original issue here was misusing ISSUE-ID instead of ID, but also
the associated username for the message should've been CN instead of DN

Change-Id: I1629c0cb7597ff2ee2867f27870378eecdafe126
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2125
Tested-by: BuildkiteCI
Reviewed-by: eta <eta@theta.eu.org>

web/panettone/src/irc.lisp

@@ -0,0 +1,26 @@
+;;;; Using irccat to send IRC notifications
+
+(in-package :panettone.irc)
+
+(defun get-irccat-config ()
+  "Reads the IRCCATHOST and IRCCATPORT environment variables, and returns them
+as two values"
+  (destructuring-bind (host port)
+      (mapcar #'uiop:getenvp '("IRCCATHOST" "IRCCATPORT"))
+    (if (and host port)
+        (values host (parse-integer port))
+        (values "localhost" 4722))))
+
+(defun send-irc-notification (body &key channel)
+  "Sends BODY to the IRC channel CHANNEL (starting with #),
+if an IRCCat server is configured (using the IRCCATHOST and IRCCATPORT
+environment variables).
+May signal a condition if sending fails."
+  (multiple-value-bind (irchost ircport) (get-irccat-config)
+    (when irchost
+      (let ((socket (socket-connect irchost ircport)))
+        (unwind-protect
+             (progn
+               (format (socket-stream socket) "~@[~A ~]~A~%" channel body)
+               (finish-output (socket-stream socket)))
+          (ignore-errors (socket-close socket)))))))