Admob Rewarded video "setUserId" API

I would like to setUserId

https://developers.google.com/android/reference/com/google/android/gms/ads/reward/RewardedVideoAd#setUserId(java.lang.String)

via cpp api because I would like to use SSV (server-side verification).

Is it possible via firebase-cpp-sdk?
Thanks

Start with the linked Android RewardedVideoAd#setUserId reference and locate the corresponding rewarded-video API surface in the Firebase C++ SDK. Check how the C++ SDK maps this Android capability and whether its existing AdMob support exposes the information needed for server-side verification. Done means the requested C++ API path and its SSV support are clearly available or documented.

Written by the indexing model from the issue text.