rfc(feature): Exception Groups

[mattjohnsonpint]

Design for changes required to support exception groups.

Rendered RFC

[mattjohnsonpint]

Yet another major rewrite of this RFC. I believe the plan is solid now 🤞 😅

Please read the revised proposal, starting from the "Proposed Solution" section. (Everything prior is as before.)

[AbhiPrasad]

This new approach looks good to me, and makes sense on the SDK side. Thanks for keeping this going @mattjohnsonpint!

[lforst]

An a posteriori learning: Extending an interface, which in itself is optional but has required fields (i.e. mechanism) is really painful. What if the exception I want to put an exception_id on doesn't have a mechanism yet? I would now have to put nonsensical default values inside mechanism to conform to the protocol again.

Maybe we should have put all the extra data onto the exception interface directly 🤔