Cache SpendProviderOutput at incentive service, send it periodically to the DS protection service

[pschuermann97]

At the moment, the deduct service sends every observed transaction to the deduct service immediately.
To provide actual offline double-spending protection, we need a cache for the observed transaction data which is periodically transferred to the double-spending protection database.

[this-kramer]

Maybe rename this to something like Cache SpendProviderOutput at incentive service, send it periodically to the DS protection service

[pschuermann97]

Agreement meeting 28.7.22: this is rather annoying for demonstration purposes (introduces artificial delay), we should just write a short remark into paper that our system supports this type of offline doublespending protection and the implementation is just a technical, not a mathematical/conceptual problem