Device tokens are a way to let one or more users access a device. A device token can be consumed in exchange of a share device association. A device token has always a device and role association. If token generation policies are defined using mqtt api the device can generate the token itself.
if one_shot is true it means that the token can be used at most once.
single_user true means that the device token is meant to be used by a single user only (the first one that is going to consume the device tonen)