Eventstream uncommittedEvents possibly overwrites events that were not committed yet

[albe]

Scenario: Retrieve the evenstream of an aggregate and keep a reference to it, adding new events to it and committing occassionally.

Expected Result: All events added to the stream are actually persisted

Actual Result: Some events are not persisted, because the uncommittedEvents array has been altered between the store.addEvents() call and the callback (async IO) and then gets overwritten with an empty array [].

Solution: Create a copy of the eventstream.uncommittedEvents array and reset the uncommitedEvents early before the IO call, then use the copy inside the callback only and re-append the uncommitted events on error.

[albe]

/cc @f3lang