[refactor] Implement the mqtt storage
[refactor] Implement the mqtt storage

LoRaWanSoFa/ttn,mgranberry/ttn,jvanmalder/ttn,TheThingsNetwork/ttn,TheThingsNetwork/ttn,jvanmalder/ttn,mgranberry/ttn,jvanmalder/ttn,LoRaWanSoFa/ttn,mgranberry/ttn,TheThingsNetwork/ttn