So this field has meaning to Firefox OS, but none of the other projects. I tossed around restricting it here, but then decided not to on the off chance that other projects would want to use this field differently. I'm not sure we gain a lot by enforcing it here and if we do it here, then mostly it just makes me write additional code to handle model saving errors and convert those to data validation errors the client will understand.

I'm on the fence about this.