[asterisk] Add direct mailbox dialing

roles/asterisk/templates/extensions.conf.j2

@@ -18,6 +18,12 @@ exten => _*XXX,1,Answer()
     same = n,VoiceMailMain(${EXTEN:1}@sailmaker)
     same = n,Hangup()
 
+;  3-digit extensions plus star go directly to voicemail
+exten => _XXX*,1,Answer()
+    same = n,Wait(1)
+    same = n,Voicemail(${EXTEN:0:-1}@sailmaker,u)
+    same = n,Hangup()
+
 ; 7+ digit calls are routed outside via the PSTN
 exten => _NXXXXXX.,1,Dial(PJSIP/pstn/${EXTEN})
     same = n,Hangup()