[renshaw]

I'm with you, in favor of strongly typed headers. Working with strings can be very error-prone; you might not catch typo bugs until your system is in production and handling some rare case for which failure is expensive.

It seems to me that, in the worst case, the downside of your current scheme is an extra field dereference, as in `request.headers.extensions.get("crazyNewField")` instead of `request.headers.get("crazyNewField")`. I think that cost is easily outweighed by the benefits.