Hello,
It would be great if someone create a plugin for playing spotify playlist via RFID cards.
There are some example code for mopidy : github.com/fsahli/music-cards
or some projects like phoniebox : github.com/MiczFlor/RPi-Jukebox-RFID
in fact i have tested this on mopidy system and working amazing,
but designed my spotify playlist cards for Volumio like that: 
so hoping to see a solution for volumio soon.
Regards