There is some neat application for example many tickets/hotel reservation/restaurant do include them and this allow to make some email clients displays these ti

There is some neat application for example many tickets/hotel reservation/restaurant do include them and this allow to make some email clients displays these tickets in a standard way. KDE Itinerary and Apple Wallet make use of this. For the KDE Itinerary part, you can read more on this here: https://volkerkrause.eu/ https://volkerkrause.eu/ (look at the KDE Itinerary posts)