My iPhone has a pre-defined "Make QR Code" "Starter Shortcut" that you can invoke by typing "Make QR Code" in Home screen search. It basically generates a QR code of the same WIFI:S:$SSID;P:$PASSWORD;; format as wificard.io.
https://en.wikipedia.org/wiki/QR_code#Joining_a_Wi%E2%80%91F...