@bruno-garcia wondering if we need to implement the JsonUnknown strategy here too (since it's the envelope bits), wdyt?

Figured it's very unlikely that the envelope and envelope item headers will change, but that's probably true for many other models as well. We can add them as well.

Figured it's very unlikely that the envelope and envelope item headers will change, but that's probably true for many other models as well. We can add them as well.

yeah lets add it then

@marandaneto done