- The class `Subscription` will internally track each `Universe`
`SubscriptionRequest` added or removed
- Adding regression test in which two different `Universe` request the
same `SubscriptionDataConfig` and one of them removes/adds it in a
toggle fashion (fails on current master)
- `UniverseSelection` pending removals will also be tracked by
`Universe`
- `UniverseDecorator` will overwrite the `Universe` member of
`SubscriptionsRequests` at `GetSubscriptionRequests()`. This is due to
`this != this,Universe`
- Adding `Subscription` unit tests covering expected behavior
- Extracting pending removals logic from `UniverseSelection` class into
a new helper class `PendingRemovalsManager`. This new class will keep
track of the `universes` requesting to remove a security. Adding unit tests
Martin Molinero