Clarify what is a delete operation

[sanderpick]

From @Gozala

• I though event delete operation needed a bit more clarification. Specifically does it imply that event body is purged?

[carsonfarmer]

What are the semantics here? For the log, this implies a tombstone event. But what about on the Store side? Do we enforce a local Store purge of the 'raw' data? Should the underlying IPFS Peer be required to drop the associated Blocks? To support an actual 'drop', we might have to think pretty carefully about how we 'rerun' an Event Log through a (set of) Reducers/Stores.

[carsonfarmer]

Here's @sanderpick's response: In threads v1, there is a native event that marks another as deleted, and then the inner nodes are unpinned (including body). Here though, where the interaction is at the higher level of the model, deletes are at the level of the Action: https://github.com/textileio/go-textile-core/blob/master/store/store.go#L50. Issue created: #47

[carsonfarmer]

Ideally data is kept and the tombstone event takes care of things, in strict compliance situations, a snapshot can be generated and the previous data can be purged from the event and block stores.