Event can still be changed during optimistic render

[tyler-dane]

Where did this happen?

Local code with an up-to-date main branch

Expected Behavior

An event shouldn't be allowed to be edited or deleted while it is being rendered optimistically

Current Behavior

During the timespan where the optimistically generated event is created and the HTTP request returns a response from the server:

The event cannot be drag and dropped
The event cannot be deleted (would delete a local version but the API would re-generate a new one after the HTTP request returns a response)

Steps to Reproduce

1. Create Event
2. Change event
3. While event change is being processed on backend, change the event again

Possible Solution

Prevent the changes while an event is optimistically rendered

Context

#197 introduced optimistic rendering.

[that-one-arab]

Assign me this please