switch back to json lohman - qtjson in new branch for more testing

src/Model/ContactItem.h

@@ -6,6 +6,7 @@
 #include <vector>
 #include <QString>
 #include "mainwindow.h"
+using json = nlohmann::json;
 
 class ContactItem
 {
@@ -33,7 +34,7 @@ public:
     void setcid(QString cid);
     void setAvatar(QString avatar);
     QString toQTString();
-    QJsonValue toJson();
+    json toJson();
 };
 
 #endif