fix(visitors): Fixes replacing visitor domain. (#14457)

* fix(visitors): Fixes replacing visitor domain.

Constructing the visitor room jid instead of doing a risky replacement.

The problem is having a room like:
[meet-jit-si-shard][email protected] and replacing with 'meet.jit.si', the dots match the -.

Author: damencho

resources/prosody-plugins/mod_visitors_component.lua

@@ -95,11 +95,13 @@ local function request_promotion_received(room, from_jid, from_vnode, nick, time
             local iq_id = new_id();
             sent_iq_cache:set(iq_id, socket.gettime());
 
+            local node = jid.node(room.jid);
+
             module:send(st.iq({
                     type='set', to = req_from, from = module.host, id = iq_id })
                 :tag('visitors', {
                     xmlns='jitsi:visitors',
-                    room = string.gsub(room.jid, muc_domain_base, req_from),
+                    room = jid.join(node, muc_domain_prefix..'.'..req_from),
                     focusjid = focus_jid })
                  :tag('promotion-response', {
                     xmlns='jitsi:visitors',
@@ -282,11 +284,13 @@ local function process_promotion_response(room, id, approved)
     local iq_id = new_id();
     sent_iq_cache:set(iq_id, socket.gettime());
 
+    local node = jid.node(room.jid);
+
     module:send(st.iq({
             type='set', to = req_from, from = module.host, id = iq_id })
         :tag('visitors', {
             xmlns='jitsi:visitors',
-            room = string.gsub(room.jid, muc_domain_base, req_from),
+            room = jid.join(node, muc_domain_prefix..'.'..req_from),
             focusjid = focus_jid })
          :tag('promotion-response', {
             xmlns='jitsi:visitors',