feat: let callers specify WireGuard interface name per tunnel

client/daemon/daemon.cpp

@@ -440,6 +440,7 @@ bool Daemon::parseConfig(const QJsonObject& obj, InterfaceConfig& config) {
   if (!obj.value("I5").isNull()) {
     config.m_specialJunk["I5"] = obj.value("I5").toString();
   }
+  config.m_ifname = obj.value("ifname").toString(WG_INTERFACE);
 
   return true;
 }

client/daemon/interfaceconfig.cpp

@@ -62,6 +62,8 @@ QJsonObject InterfaceConfig::toJson() const {
   }
   json.insert("vpnDisabledApps", disabledApps);
 
+  json.insert("ifname", m_ifname);
+
   return json;
 }
 

client/daemon/interfaceconfig.h

@@ -57,6 +57,7 @@ class InterfaceConfig {
   QString m_underloadPacketMagicHeader;
   QString m_transportPacketMagicHeader;
   QMap<QString, QString> m_specialJunk;
+  QString m_ifname;
 
   QJsonObject toJson() const;
   QString toWgConf(