- [x] Optimize `select_inputs_from_accounts` to return a single change operation instead of a vector
- [ ] Write cache layer on top of the storage layer, specially if accounts are settled
- [ ] Improve read performance with SQLite
- [ ] Add a locking mechanism, to either a start a tx per account, or use the storage engine as a lock mechanism (to lock the utxos)
- [ ] Add ability to query accounts in a point in time
- [ ] Write other servers, other than the restful server
- [ ] Add caching layer: This cache layer can built on top of the utxo::ledger, because all operations can be safely cached until a new transaction referencing their account is issued, by that point, all the caches related to anaccount can be evicted
- [ ] Build admin interface
- [ ] Add memo to changes. Build append only table with all movements as
      inserts. Wraps the objects to all their changes