Messages to room participants are forwarded to the IRC user

For example, both JID #chan%server@biboumi/Toto and toto!server@biboumi are
equivalent, except that if you send a message to the first one, subsequent
messages coming from the user toto will come from that same JID. This is
done to be consistent for the XMPP user, and respond from the same JID than
the 'to' of the first message.

fix #2468

src/bridge/bridge.hpp

@@ -123,6 +123,14 @@ public:
    * Get the number of server to which this bridge is connected or connecting.
    */
   size_t active_clients() const;
+  /**
+   * Add (or replace the existing) <nick, jid> into the preferred_user_from map
+   */
+  void set_preferred_from_jid(const std::string& nick, const std::string& full_jid);
+  /**
+   * Remove the preferred jid for the given IRC nick
+   */
+  void remove_preferred_from_jid(const std::string& nick);
 
 private:
   /**
@@ -157,6 +165,14 @@ private:
    * their sockets.
    */
   std::shared_ptr<Poller> poller;
+  /**
+   * A map of <nick, full_jid>. For example if this map contains <"toto",
+   * "#somechan%server@biboumi/ToTo">, whenever a private message is
+   * received from the user "toto", instead of forwarding it to XMPP with
+   * from='toto!server@biboumi', we use instead
+   * from='#somechan%server@biboumi/ToTo'
+   */
+  std::unordered_map<std::string, std::string> preferred_user_from;
 
   Bridge(const Bridge&) = delete;
   Bridge(Bridge&& other) = delete;