Migrate /vip to Helix API (#4010)

Fixes #3983 

Co-authored-by: iProdigy <iProdigy@users.noreply.github.com>
Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

tests/src/HighlightController.cpp

@@ -249,6 +249,14 @@ public:
                       failureCallback)),
                 (override));
 
+    // The extra parenthesis around the failure callback is because its type contains a comma
+    MOCK_METHOD(
+        void, addChannelVIP,
+        (QString broadcasterID, QString userID,
+         ResultCallback<> successCallback,
+         (FailureCallback<HelixAddChannelVIPError, QString> failureCallback)),
+        (override));
+
     MOCK_METHOD(void, update, (QString clientId, QString oauthToken),
                 (override));
 };