Add support for event ID generation

[esammer]

No description provided.

[esammer]

We're probably going to want to shade this to prevent issues for users.

[joey]

I'd rather implement ID generation using the builder pattern rather than including the static populateId() method. The only use case for the static method is for modifying the ID in place. I could maybe see that as useful if you're upgrading to a new standard and want to apply a new ID generation technique to data sent over the wire using the older standard. Then again, you could have the builder take in an existing Event to seed the fields at the cost of allocating a new Event object.

[esammer]

Thanks for the feedback. The only challenge I see with the custom builder is that we'd have to supply our own templates for Avro code gen so we could sneak it in to the generated class. Does that sound awful or like a reasonable solution? Or, is my OCD working overtime and it's fine for the builder to live outside of the Event class (which, admittedly, I don't like)?

[joey]

I'd probably have the builder live outside the Event class, but maybe that's because I'm nervous when messing with code gen stuff. Does Avro code gen support giving them templates? If so, I'd be down to use that.