Do not change the nick when joining a second room with a different nick

As the doc says, the nick changes must be explicit in an already joined
room, and not when joining a room.

src/bridge/bridge.cpp

@@ -393,8 +393,12 @@ void Bridge::leave_irc_channel(Iid&& iid, const std::string& status_message, con
     }
 }
 
-void Bridge::send_irc_nick_change(const Iid& iid, const std::string& new_nick)
+void Bridge::send_irc_nick_change(const Iid& iid, const std::string& new_nick, const std::string& requesting_resource)
 {
+  // We don’t change the nick if the presence was sent to a channel the resource is not in.
+  auto res_in_chan = this->is_resource_in_chan(ChannelKey{iid.get_local(), iid.get_server()}, requesting_resource);
+  if (!res_in_chan)
+    return;
   IrcClient* irc = this->get_irc_client(iid.get_server());
   irc->send_nick_command(new_nick);
 }

src/bridge/bridge.hpp

@@ -80,7 +80,7 @@ public:
   void send_private_message(const Iid& iid, const std::string& body, const std::string& type="PRIVMSG");
   void send_raw_message(const std::string& hostname, const std::string& body);
   void leave_irc_channel(Iid&& iid, const std::string& status_message, const std::string& resource);
-  void send_irc_nick_change(const Iid& iid, const std::string& new_nick);
+  void send_irc_nick_change(const Iid& iid, const std::string& new_nick, const std::string& requesting_resource);
   void send_irc_kick(const Iid& iid, const std::string& target, const std::string& reason,
                      const std::string& iq_id, const std::string& to_jid);
   void set_channel_topic(const Iid& iid, const std::string& subject);

src/xmpp/biboumi_component.cpp

@@ -149,7 +149,7 @@ void BiboumiComponent::handle_presence(const Stanza& stanza)
         {
           const std::string own_nick = bridge->get_own_nick(iid);
           if (!own_nick.empty() && own_nick != to.resource)
-            bridge->send_irc_nick_change(iid, to.resource);
+            bridge->send_irc_nick_change(iid, to.resource, from.resource);
           const XmlNode* x = stanza.get_child("x", MUC_NS);
           const XmlNode* password = x ? x->get_child("password", MUC_NS): nullptr;
           bridge->join_irc_channel(iid, to.resource, password ? password->get_inner(): "",