This was originally used for a more compact vCard representation, but today is mostly relevant for Wifi configuration QR codes.
See https://en.wikipedia.org/wiki/MeCard_(QR_code) and https://github.com/zxing/zxing/wiki/Barcode-Contents#wi-fi-network-config-android-ios-11
Lifted from QRCA for use in other places, such as plasma-nm.