- Have users be an array. Mirror storage events of a shard that multiple users
  have uploaded will have multiple users interested. This will provide an ability
  to track how long the mirror should be held. When one user deletes the shard,
  the user will be removed from the storage event. When there is only one user
  the storeEnd will be updated to terminate the storage of the shard.
- Seperate user and client, thus it's possible to have a client and user
  for mirror actions, so that it's possible to query storage events of mirrors
  by a user.

- Mirrors will be created without a user and only a client
- Queries can fold all storage events based on the hash and determine all users and storage time frames

```
z = 0.9999 // target percentage
y = 5 // number of nodes
z = 0.841510681 // node percentage
--------
1 - ((1 - x) ^ y) = z
--------
1 = z + ((1 - x) ^ y)
--------
1 - z = (1 - x) ^ y
--------
(1 - z) ^ 1/y = 1 - x
--------
1 - ((1 - z) ^ 1/y) = x
--------
```

Meeting notes:
https://github.com/Storj/dev-meetings/blob/master/2017-12-06-summary.md

This is to make sure that the cron service is able to not repeat
proccessing over storage events that have already been processed.
While this doesn't cause an issue with resolving the event, it will
contribute to incorrect rates of reports being saved to the user,
in the case that an event is process more than one time.

We were already updating both timestamps at the same time anyways so
having two values was unnecessary.