added user handling

src/main/java/de/geofroggerfx/model/User.java

@@ -60,4 +60,20 @@ public class User {
     public void setName(String name) {
         this.name.set(name);
     }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        User user = (User) o;
+
+        return id.equals(user.id);
+
+    }
+
+    @Override
+    public int hashCode() {
+        return id.hashCode();
+    }
 }