Edit or delete event (after it's been synced)

[lalomartins]

Events in the event server sense are immutable, but events in the sense of things that happen in real life and we record in the app sometimes get recorded incorrectly and need to be corrected. For this, we'll use a separate event category weekly goals correction; the timestamp is the timestamp of the original event for easier filtering, and the data goes in additional; {uuid: 'original_event_uuid', values: 'new_values', timestamp: time_of_change}, or for deleting, instead of a values key, a cancel: true.

(What about changing the timestamp, especially when it crosses a day boundary? Maybe better to cancel and replace?)