Immutable event builder

[fabiojose]

Implements an immutable event builder, to builds events instances that are unchangeable after its build.

Depends on #28

[lance]

@fabiojose I agree that events should probably be immutable - aside from a well-defined path for converting from/to spec versions. Given how the repo has been evolving, how do you think this issue should progress?

[grant]

how do you think this issue should progress?

If we use JSON for CloudEvents, then we can just Object.freeze our event data to make it immutable.

Requires #65.

[lance]

I'm going to mark this a stalled for now. TypeScript users now have Object.freeze for regular objects. However, that doesn't work for the CloudEvent class. We'd need to add a freeze() method to the class itself to prevent modification. This is because the setters on the class delegate to this.spec.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 5 days

[grant]

Marking all CloudEvent fields as readonly should be a solution.

This is very common and recommended in TypeScript. See vscode's source for examples.