Push notifications in multiple devices

[dolcalmi]

when a user log in in a new device the notifications are sent to the old one.

We should guarantee that only 1 device id/token is related to 1 user

Possible solutions:

• Remove previous device id/tokens when a user log in to its account
• Remove all device id/tokens related to a user when logouts

[nicolasburtey]

problem still present