For a quick fix, the app Halide on the app store enables portrait mode on objects. I downloaded it and it has made me so happy. Hopefully Apple updates their camera to do this one day. In the meantime, this $5.99 app is totally worth it!
Halide Camera by Chroma Noir LLC https://itunes.apple.com/us/app/halide-camera/id885697368?mt=8&at=10l3Vy
Halide Camera by Chroma Noir LLC https://itunes.apple.com/us/app/halide-camera/id885697368?mt=8&at=10l3Vy