User portfolio snapshot
Snapshot creates PIT (point in time) state of user portfolio.
Created snapshot contains a list off all assets and price of
assets at time of creation. It is persistent.
User can create x snapshots.
Snapshots can be compared in user analytical/reporting interface.
Analytical interface provides metrics:
- volume between snapshots
- value between snapshots
- deposits/withdrawals made in that time
- projection between PIT and current time
- ...