Decode incoming JIDs local part according to xep 0106

This let users send message to nicks such as Q@CServe.quakenet.org

fix #3047

src/irc/iid.cpp

@@ -1,5 +1,6 @@
 #include <utils/tolower.hpp>
 #include <config/config.hpp>
+#include <utils/encoding.hpp>
 
 #include <irc/iid.hpp>
 
@@ -68,6 +69,7 @@ Iid::Iid():
 void Iid::set_local(const std::string& loc)
 {
   this->local = utils::tolower(loc);
+  xep0106::decode(local);
 }
 
 void Iid::set_server(const std::string& serv)

src/test.cpp

@@ -396,7 +396,15 @@ int main()
     assert(iid6.get_server() == "fixed.example.com");
     assert(iid6.is_channel);
     assert(!iid6.is_user);
+
+    Config::set("fixed_irc_server", "", false);
   }
 
+  std::cout << color << "Testing JID (xep 0106) decoding…" << reset << std::endl;
+  assert(Iid{"space\\20cadet!"}.get_local() == "space cadet");
+  assert(Iid{"call\\20me\\20\\22ishmael\\22!"}.get_local() == "call me \"ishmael\"");
+  assert(Iid{"\\2f.fanboy!"}.get_local() == "/.fanboy");
+  assert(Iid{"Q\\40CServe.quakenet.org!"}.get_local() == "q@cserve.quakenet.org");
+
   return 0;
 }