If, for whatever reason, you wanted to do this with older iOS you had to use a configuration profile[2]. This would be distributed as a PList that you'd link to in the QR code. Which means the device needs to be connected to a network to download it first. A captive portal could help with that, or put it on the internet maybe protected with a geofence so you're not advertising your password to the world.
https://play.google.com/store/apps/details?id=com.google.zxi...